You look unhappy， my son?—I’m wondering how long it’ll be we come to China again.

I could look after ____ when I was five.— Really? I can’t believe it.

Where are you going __________ your next vacation?-We decided __________ Europe.[ ]

What are you doing ______ vacation? —I’m going fishing. [ ]

I want to write __________ article about the great inventors in the world. Can you help me?–Sorry, I don’t know much about __________ topic.