不错,都是强调句。
It was Mary that Mr Green give a birthday present to.
这句强调的是生日礼物接受者mary
变成正常的陈述句就是
Mr Green gives a birthday present to Mary
第二句
it was the present that his mother sent him
这句强调的是礼物。
变成正常的陈述句就是
His mother sents him a present.
都是,强调这个礼物是他的妈妈送的。第一句意为格林先生送礼物的对象是玛丽
强调句。