I think this is ___ useful book, so I will keep it for ever.
________ we go swimming in Xishuanghu Lake today? —- Oh, no. It’s ________ cold to swim on such days. I will catch a cold.
I can’t decide______. – You mean the red one or the blue one?
Try again, maybe you will come up with a better idea.
.—I can’t find Mr. Smith. Where did you last see him this morning?—It was in the hotel _______ he stayed.