Поставить в Present Perfect Continuous.

1. My friend in the library since 9 o'clock (have been staying; has been staying) 2. Tom … cigarettes for 20 years (have been smoking; has been smoking)

Переведите предложения с русского на английский, используя Present Perfect или Present Perfect Continuous.
1. Целый вечер я печатаю. Я уже напечатала 20 страниц.
2. Мы пишем контрольную работу уже 50 минут. Некоторые студенты уже закончили ее.
3. Ты давно ждешь меня? Нет, я только что пришел.
4. Чем вы занимались сегодня утром? Сажали деревья в саду. Сколько деревьев вы посадили? Девять.
5. Я перевожу статью уже два часа, но еще не перевела ее.
6. Хирург делает операцию уже три часа, но еще не закончил ее.

1. My friend has been staying in the library since 9 o'clock.
In this sentence, we use the Present Perfect Continuous tense to show that the action of staying in the library started in the past (at 9 o'clock) and is still happening in the present.

2. Tom has been smoking cigarettes for 20 years.
Here, we also use the Present Perfect Continuous tense to indicate that the action of smoking cigarettes started in the past (20 years ago) and is still ongoing in the present.

Now let's translate the sentences from Russian to English using the Present Perfect or Present Perfect Continuous tense:

1. I have been typing for the whole evening. I have already typed 20 pages.
In this translation, we use the Present Perfect Continuous tense to express the ongoing action of typing that started in the past (the whole evening) and is still continuing in the present (not yet finished).

2. We have been writing the test for 50 minutes. Some students have already finished it.
Here, we use the Present Perfect Continuous tense to indicate the ongoing action of writing the test that started in the past (for 50 minutes) and is still happening in the present. We also use the Present Perfect tense to show that some students have already completed it.

3. Have you been waiting for me for a long time? No, I have just arrived.
In this sentence, we use the Present Perfect Continuous tense to ask about the ongoing duration of waiting (for a long time) that started in the past and is still going on. The negative answer is given using the Present Perfect tense to show the action of arriving has just happened.

4. What have you been doing this morning? We have been planting trees in the garden. How many trees have you planted? Nine.
Here, we use the Present Perfect Continuous tense to ask about the ongoing activities (what have you been doing) that started in the past (this morning) and are still happening. The answer uses the Present Perfect tense to state the action of planting trees and the number of trees planted.

5. I have been translating the article for two hours, but I haven't finished it yet.
In this sentence, we use the Present Perfect Continuous tense to describe the ongoing action of translating the article that started in the past (for two hours) and is still in progress (not yet completed).

6. The surgeon has been performing the operation for three hours, but he hasn't finished it yet.
Here, we use the Present Perfect Continuous tense to indicate the ongoing action of performing the operation that started in the past (for three hours) and is still ongoing (not yet completed).