11. choose the appropriate tense. 1 .i belleve/will believe it when i see/ am seeing it. 2. she usually has / is having two cups of coffee, but today she has/ is having only one 3. if you drop / will drop that vase, it wil hreak /break. 4. when i wrote / was writing my essay, john called / was calling me. 5. i'we done / did that task already 6. by the end of next week i will have alreody left/ will leave this city 7. when i was going/went out of the house, i took my umbrella because it nained /was raining. 8. about a thousand people vere waiting / waired in front of the embassy 9. it has snowed/has been snowing since friday 10. i know/have kmuun adrian fora very long time.

1. I will believe it when I see it.
Explanation: The correct tense to use in this sentence is the future simple tense (will believe) because the action of believing will happen after the action of seeing.
Step-by-step solution: First, identify the subject and verb in the sentence. The subject is "I" and the verb is "believe". Next, determine the appropriate tense. Since the action of believing will happen after the action of seeing, the future simple tense "will believe" is used. Finally, choose the correct form of the verb "see" in the same tense. In this case, it is "see" (without the "s" at the end) because the subject is "I".
2. She usually has two cups of coffee, but today she is having only one.
Explanation: The correct tense to use in this sentence is the present continuous tense (is having) because the action of having coffee is happening now.
Step-by-step solution: First, identify the subject and verb in the sentence. The subject is "she" and the verb is "has". Next, determine the appropriate tense. Since the action of having coffee is happening now, the present continuous tense "is having" is used. Finally, choose the correct form of the verb "have" in the same tense. In this case, it is "is having" because the subject is "she".
3. If you drop that vase, it will break.
Explanation: The correct tense to use in this sentence is the future simple tense (will break) because the action of breaking the vase will happen after the action of dropping it.
Step-by-step solution: First, identify the subject and verb in the sentence. The subject is "it" and the verb is "break". Next, determine the appropriate tense. Since the action of breaking the vase will happen after the action of dropping it, the future simple tense "will break" is used. Finally, choose the correct form of the verb "drop" in the same tense. In this case, it is "drop" (without the "s" at the end) because the subject is "you".
4. When I was writing my essay, John was calling me.
Explanation: The correct tense to use in this sentence is the past continuous tense (was writing, was calling) because both actions were happening simultaneously in the past.
Step-by-step solution: First, identify the subject and verb in each part of the sentence. The subject is "I" and the verb is "write" in the first part, and the subject is "John" and the verb is "call" in the second part. Next, determine the appropriate tense for each part. Since both actions were happening simultaneously in the past, the past continuous tense "was writing, was calling" is used. Finally, choose the correct form of the verbs "write" and "call" in the same tense. In this case, it is "was writing" and "was calling" because the subjects are "I" and "John" respectively.
5. I have done that task already.
Explanation: The correct tense to use in this sentence is the present perfect tense (have done) because the action of completing the task happened before now.
Step-by-step solution: First, identify the subject and verb in the sentence. The subject is "I" and the verb is "have done". Next, determine the appropriate tense. Since the action of completing the task happened before now, the present perfect tense "have done" is used. Finally, choose the correct form of the verb "do" in the same tense. In this case, it is "done" because the subject is "I".
6. By the end of next week, I will have already left this city.
Explanation: The correct tense to use in this sentence is the future perfect tense (will have left) because the action of leaving the city will happen before a specified time in the future.
Step-by-step solution: First, identify the subject and verb in the sentence. The subject is "I" and the verb is "will have left". Next, determine the appropriate tense. Since the action of leaving the city will happen before the specified time (end of next week), the future perfect tense "will have left" is used. Finally, choose the correct form of the verb "leave" in the same tense. In this case, it is "left" because the subject is "I".
7. When I went out of the house, I took my umbrella because it was raining.
Explanation: The correct tense to use in this sentence is the simple past tense (went, was raining) because both actions happened in the past.
Step-by-step solution: First, identify the subject and verb in each part of the sentence. The subject is "I" and the verb is "go" in the first part, and the subject is "it" and the verb is "rain" in the second part. Next, determine the appropriate tense for each part. Since both actions happened in the past, the simple past tense "went, was raining" is used. Finally, choose the correct form of the verbs "go" and "rain" in the same tense. In this case, it is "went" and "was raining" because the subjects are "I" and "it" respectively.
8. About a thousand people were waiting in front of the embassy.
Explanation: The correct tense to use in this sentence is the past continuous tense (were waiting) because the action of waiting was happening in the past.
Step-by-step solution: First, identify the subject and verb in the sentence. The subject is "people" and the verb is "wait". Next, determine the appropriate tense. Since the action of waiting was happening in the past, the past continuous tense "were waiting" is used. Finally, choose the correct form of the verb "wait" in the same tense. In this case, it is "were waiting" because the subject is "people" (plural).
9. It has been snowing since Friday.
Explanation: The correct tense to use in this sentence is the present perfect continuous tense (has been snowing) because the action of snowing started in the past and is still happening now.
Step-by-step solution: First, identify the subject and verb in the sentence. The subject is "it" and the verb is "snow". Next, determine the appropriate tense. Since the action of snowing started in the past and is still happening now, the present perfect continuous tense "has been snowing" is used. Finally, choose the correct form of the verb "snow" in the same tense. In this case, it is "has been snowing" because the subject is "it".
10. I have known Adrian for a very long time.
Explanation: The correct tense to use in this sentence is the present perfect tense (have known) because the action of knowing Adrian started in the past and continues until now.
Step-by-step solution: First, identify the subject and verb in the sentence. The subject is "I" and the verb is "know". Next, determine the appropriate tense. Since the action of knowing Adrian started in the past and continues until now, the present perfect tense "have known" is used. Finally, choose the correct form of the verb "know" in the same tense. In this case, it is "have known" because the subject is "I".