keep safe与protect有区别吗?

几道英语问题 求详解
To keep safe ------ an earthquake,you should remain at a spot in your yoom where nothing may fall on you .
A.in searth of B. in advance of C. in terms of D.in case of

-Have you known each other for long?
-Not very long ,--------we started to work in theABC Motor Company
答案是since，为什么不能用after

If you have to catch the first bus every day,choose this hotelIt is very -----for the station.
A.close B.comfortable C.convenient D.near

The shop owner promised me that he would inform me as soon as the product became -------.
A.approachable B.affordable C.available D.accessible
P.S A D.有什么区别

When I got home,i found the door open.A terrible thought ------me that someone broke into my house.
A.beat B. struck C.knocked D.hit