Our teacher makes _____easier for us to unterstand the sentences.A.this B.that C.it D.its

C，这里it是做形式宾语，真正的宾语是to unterstand the sentences，又由于用的多了，成了一种较固定的搭配，make it +形容词+for sb. to do sth.
当主语或宾语较长时，it 常常用作形式主语或形式宾语，如 It's impossible (for us) to get there in time. （我们）不可能及时赶到那里. She finds it boring staying/to stay at home. 她觉得待在家中很无聊

答案应该是C, 是一种常用句型。

C,make it easier for sb to do sth(固定句型）,表示让某人更易采取行动

选D