Open the brackets: When we came to the station, the train already (to arrive), the passengers (to hurry) to occupy their seats..

Look! The children (to fight) again.

A vegetarian is a person who (not to eat) meat.

The students (to finish) the test by 4 p.m. tomorrow.

You look gloomy! What's the matter?-i (to lose) my keys.

Call me tomorrow at 10.1 (not to sleep ) at that time.

Last year I met an old friend of mine whom I (not to see) for years

Nick was hot out of breath. He (to run) for 2 hours.

Why is granny so anxious? - She can't find her glasses. She (to look) for them for half an hour already.

When you (to buy) this watch?

1. When we came to the station, the train had already arrived, the passengers were hurrying to occupy their seats.
Explanation: The sentence is in past simple tense. "Came" is the past simple form of "come". "Had already arrived" is the past perfect tense of the verb "arrive". "Were hurrying" is the past continuous tense of the verb "hurry".

2. Look! The children are fighting again.
Explanation: The sentence is in present continuous tense. "Look" is a command verb, meaning to pay attention. "Are fighting" is the present continuous tense of the verb "fight".

3. A vegetarian is a person who does not eat meat.
Explanation: The sentence is in present simple tense. "Is" is the present simple form of the verb "be". "Does not eat" is the present simple tense of the verb "eat".

4. The students will finish the test by 4 p.m. tomorrow.
Explanation: The sentence is in future simple tense. "Will finish" is the future simple tense of the verb "finish". "By 4 p.m. tomorrow" indicates the time frame.

5. You look gloomy! What's the matter? - I have lost my keys.
Explanation: The sentence is in present perfect tense. "Look" is the present simple form of the verb "look". "Have lost" is the present perfect tense of the verb "lose". "Have" is used as an auxiliary verb to show the action has happened in the past and has a connection to the present.

6. Call me tomorrow at 10.1, I will not be sleeping at that time.
Explanation: The sentence is in future simple tense. "Call" is a command verb, meaning to make a phone call. "Will not be sleeping" is the future continuous tense of the verb "sleep".

7. Last year I met an old friend of mine whom I had not seen for years.
Explanation: The sentence is in past simple and past perfect tense. "Met" is the past simple form of the verb "meet". "Had not seen" is the past perfect tense of the verb "see".

8. Nick was hot out of breath. He had been running for 2 hours.
Explanation: The sentence is in past simple and past perfect continuous tense. "Was" is the past simple form of the verb "be". "Had been running" is the past perfect continuous tense of the verb "run".

9. Why is granny so anxious? - She can't find her glasses. She has been looking for them for half an hour already.
Explanation: The sentence is in present simple and present perfect continuous tense. "Is" is the present simple form of the verb "be". "Can't find" is the present simple tense of the verb "find". "Has been looking" is the present perfect continuous tense of the verb "look".

10. When did you buy this watch?
Explanation: The sentence is in past simple tense. "Did buy" is the past simple tense of the verb "buy". "When" is used to ask about the specific time.