Sorry. Madam. You’d better come tomorrow because it’s______the visiting hours.   

They sometimes go on working ____ the light of the moon.

I’m quite familiar ___ the writer who wrote these songs.

 — __________ when has the country been open to international trade?— 1978, I suppose. 

________cleaning the yard and making up the beds for the  old，we also read newspapers for them and had chats with them.