1. Paul reads the newspaper by/at the beginning of the day. 2.She started her career in/at teaching when she
was twenty-three years old. .
3 The teacher left Elliot in/at charge of the class
while she was in the headmaster's office.
4 There are very few people who can work well
on/ under great pressure.
5 He left school at/on the age of sixteen.
6 Everyone congratulated him in/at the end of his
lecture.​

1. Paul reads the newspaper at the beginning of the day.

Explanation: "At" is used to indicate a specific point or time, such as the beginning of the day. In this sentence, it means that Paul reads the newspaper when the day starts.

2. She started her career in teaching when she was twenty-three years old.

Explanation: "In" is used to indicate a specific period of time. In this sentence, it means that she began her career during the time period of teaching, which started when she was twenty-three years old.

3. The teacher left Elliot in charge of the class while she was in the headmaster's office.

Explanation: "In" is used to indicate a specific location or situation. In this sentence, it means that the teacher left Elliot in the situation or position of being in charge of the class while she was in the headmaster's office.

4. There are very few people who can work well under great pressure.

Explanation: "Under" is used to indicate being subjected to something. In this sentence, it means that there are very few people who can work well when subjected to the condition or situation of great pressure.

5. He left school at the age of sixteen.

Explanation: "At" is used to indicate a specific point or time. In this sentence, it means that he left school when he reached the age of sixteen.

6. Everyone congratulated him at the end of his lecture.

Explanation: "At" is used to indicate a specific point or time. In this sentence, it means that everyone congratulated him when the lecture came to an end.