当表示“......的入口”时，最常见的用法是 the entrance to ：

1. The entrance to the hall is on your right. 大厅的人口在你的右方。

2. The entrance to the cave had been blocked up. 山洞的人口已堵塞。

3. She was sitting at the entrance to the museum. 她坐在博物馆的入口处。

但是，当说话者把 the entrance 看作是某个事物的一部分时，也可以使用  the entrance of 。例如：

1. In the end we got back to the entrance of the forest, but we did not see Sun Yan. 最后，我们回到了森林的入口处，但是我们没看到孙尧。

2. The explosion did a good deal of damage to the entrance of the building.  爆炸对建筑物的人口造成了很大破坏。

（以上摘自赵振才：《英语常见问题解答大词典》增订版第五版p.436）

the entrance to A（A的入口处/大门口）  类似于 the key to the door（门的钥匙）;  the answer to the question（问题的答案）

(1) the key to the door 门的钥匙

I have lost the key to the door.  我丢了门的钥匙.

Can I have the key to the door, please?  能把前门的钥匙给我吗?

(2)the answer to question 问题的答案

 Please hands up if you know the answer to the question.  如果你们知道这个问题的答案,请举手.

Can anyone tell me the answer to the question?  有谁可以告诉我这个问题的答案?

(3) the entrance to sth  某个地方的入口

Where is the entrance to the museum 博物馆入口处在哪里？

Beside the entrance to the church, turn right.在教堂入口旁向右转。

A lighthouse marks the entrance to the harbour.灯塔是进入海港航道的标志。

备注：entrance to sth还可以表示“到某地进入权/ 进入许可 或者进入资格”

They were refused entrance to the exhibition.他们被拒于展览会门外。

The police were unable to gain entrance to the house.警方怎么也进不去这栋房子。

Entrance to the golf club is by sponsorship only.只有有人担保才能加入这个高尔夫俱乐部。

Hewitt had gained entrance to the Hall by pretending to be a heating engineer. 休伊特装扮成供热工程师从而进入大厅。

Entrance to universities and senior secondary schools was restricted. 进入大学或高中的资格受到限制。