1,两句不相等.
They are my friend.他们是我的朋友.
They are my friend's 它们是我朋友的.
2,这两个句子相等,但是并不是在所有的情况下,这两种句型都相等.
there are seven days in a week.一周之内有七天.
A week has seven days.一周有七天.
第一个句子的“有”侧重存在,第二个句子的有,侧重“拥有”.
3,两句不相等.
Mr Green has three children.格林先生有三个小孩.
Mr Green has three children's.这个句子是错误的.