Sir, I have a few doubts... Could you please give the correct answer for these questions?
FILL IN THE BLANKS WITH SUITABLE FORMS OF THE VERBS GIVEN IN THE BRACKETS
1) We —— on the project since last week. (work)
2) I —— the picture this morning. ( draw)
3) The children—— (enter) the stage before the curtain ——(go) up.

CHANGE FROM ACTIVE TO PASSIVE VOICE
1) All his friends laughed at him

1) We —— on the project since last week. (work)
We have been working on this project since last week.
2) I —— the picture this morning. ( draw)
 I drew this picture this morning.
3) The children—— (enter) the stage before the curtain ——(go) up.
 The children had entered the stage before the curtain went up.

CHANGE FROM ACTIVE TO PASSIVE VOICE
1) All his friends laughed at him
 He was laughed at by all his friends.