1. They NOT ARRIVE yet.2. When I entered the room, theyWATCH TV.3.1ATTEND dance classes since I was a child.4. They took a rest after theyCLEAN UP the house.5. HeRAISE his hand to welcome us.6. I'll give the magazine back as soon as heNEED it.7. If itNOT RAIN, we will have the party in the park.8. When I arrived at the restaurant, MaryGO home.9. Is that the man youlMEET yesterday?10. SheHAVE a marvelous bag to go with the dress.11.1NOT SEE you for 3 years.12. Don't go out. ItRAIN cats and dogs.​

1. They have not arrived yet.
Explanation: "Not" is used to negate the verb "arrive". The present perfect tense is used to indicate that the action of arrival has not happened up to now.

2. When I entered the room, they were watching TV.
Explanation: "Were" is the past continuous tense of the verb "be" used to describe an ongoing action in the past. "Watching" is the present participle form of the verb "watch".

3. I have been attending dance classes since I was a child.
Explanation: The present perfect continuous tense is used to indicate an action that started in the past and is still ongoing. "Have been attending" is the present perfect continuous form of the verb "attend".

4. They took a rest after they had cleaned up the house.
Explanation: "Had cleaned" is the past perfect tense of the verb "clean". The past perfect tense is used to indicate an action that happened before another action in the past.

5. He raised his hand to welcome us.
Explanation: "Raised" is the past tense of the verb "raise". It indicates a completed action in the past.

6. I'll give the magazine back as soon as he needs it.
Explanation: "Needs" is the simple present tense of the verb "need". It indicates a general truth or habitual action.

7. If it doesn't rain, we will have the party in the park.
Explanation: "Doesn't" is the simple present tense of the verb "do not". It is used to form the negative in the conditional sentence. "Will have" is the future simple tense of the verb "have".

8. When I arrived at the restaurant, Mary had gone home.
Explanation: "Had gone" is the past perfect tense of the verb "go". It indicates an action that happened before another past action.

9. Is that the man you met yesterday?
Explanation: "Met" is the past tense of the verb "meet". It indicates a completed action in the past.

10. She has a marvelous bag to go with the dress.
Explanation: "Has" is the simple present tense of the verb "have". It is used to indicate possession.

11. I haven't seen you for 3 years.
Explanation: "Haven't seen" is the present perfect tense of the verb "see". It is used to indicate an action that started in the past and still has an effect in the present.

12. Don't go out. It's raining cats and dogs.
Explanation: "Is raining" is the present continuous tense of the verb "rain". It indicates an ongoing action at the present moment.