1.This is a tomato.(改为复数)These are tomatoes.
2.His joke made everyone laugh.(laugh)
（make为使役动词,后接动词原形）
3.It's seven o'clock now.The Blacks are having (have) breakfast.
定冠词the加上姓氏的复数,表“夫妇两人”或“一家人”,作主语时,谓语动词不能用单数.
4.Please be quiet (quiet) in the library and read quietly (quiet)
5.The door is open (open),buy nobody is in the room
open在此为形容词,“开着的,开放的”
6.our(反义词) (这个单词你是不是写错了,out?out in)
twelfth(基数词) twelve