12. When I (walk) into the office, several people(watch) news on CNN.13. They..meet) my parents at eight this moming14. The salesman(help) the customer when the thief(come) into the store.15. While I(study), she(cook16. Children(talk), when I..(fall) asleep17. What.(she.do) during her holiday last month?18. While I(take ) a bath, Suze..(fix) thedoor19. Yesterday we(play) at the park. I(throw) the wood stick and mydog...(catch) it for me.20. What..(you, do) during the Math class thismorning?​

12. When I walk into the office, several people are watching news on CNN.
Explanation: The verb "walk" shows an action in the present tense, so we use the present continuous tense "are watching" to describe an action that is happening at the moment.

13. They met my parents at eight this morning.
Explanation: The verb "meet" is in the past tense, so we use the simple past tense "met" to describe an action that happened in the past.

14. The salesman was helping the customer when the thief came into the store.
Explanation: The verb "help" is in the past continuous tense, so we use the past continuous tense "was helping" to describe an ongoing action in the past. The verb "come" is in the past tense, so we use the simple past tense "came" to describe an action that happened in the past.

15. While I was studying, she was cooking.
Explanation: The verb "study" is in the past continuous tense, so we use the past continuous tense "was studying" to describe an ongoing action in the past. The verb "cook" is also in the past continuous tense, so we use "was cooking" to describe another ongoing action in the past.

16. Children were talking when I fell asleep.
Explanation: The verb "talk" is in the past continuous tense, so we use the past continuous tense "were talking" to describe an ongoing action in the past. The verb "fall" is in the past tense, so we use the simple past tense "fell" to describe an action that happened in the past.

17. What did she do during her holiday last month?
Explanation: The verb "do" is in the past tense, so we use the simple past tense "did" to describe an action that happened in the past.

18. While I was taking a bath, Suze was fixing the door.
Explanation: The verb "take" is in the past continuous tense, so we use the past continuous tense "was taking" to describe an ongoing action in the past. The verb "fix" is also in the past continuous tense, so we use "was fixing" to describe another ongoing action in the past.

19. Yesterday we played at the park. I threw the wood stick and my dog caught it for me.
Explanation: The verb "play" is in the past tense, so we use the simple past tense "played" to describe an action that happened in the past. The verb "throw" is also in the past tense, so we use "threw" to describe an action that happened in the past. The verb "catch" is also in the past tense, so we use "caught" to describe an action that happened in the past.

20. What did you do during the Math class this morning?
Explanation: The verb "do" is in the past tense, so we use the simple past tense "did" to describe an action that happened in the past.