1.Once day they _found__[find]a mirror for the first time and they saw what they_looked_[look]like?
once day 曾经有一天,用过去时
2.The girl did not like what her brother said and _gave_[give]him a hard push."_Go_[go]away!"she said.
gave是和前面的did not like 并列的,后面是祈使句,用一般式
3.Their father saw what_has happened_[happen].He went up to them and_said_[say]to the boy.
已经发生了,且对现在造成影响,所以用现在完成式,后面的是与went 并列的
4.Then he said to the girl,"My dear,if you help everyone and do your best_to make_[make]him or her happy,everyone_will like_[like]you.
固定词组搭配 do one's best to do
后面是因为if引导的条件状语从句,主将从现