根据对话情景，填入恰当的单词。（每空一词，每词1分，共6分）
A: Hi! May I speak to Sam, please? I have something for him.
B: Speaking, please. This is Sam.
A: Sam, I haven’t seen you for long. Where have you (____)?
B: I am at home all the time because of my illness. What’s up?
A: It’s about volunteer work. Would you like to join us?
B. (____), I’d love to. When and where?
A: It’s on Sunday in the hospital. We’ll go together to (__) up the sick kids.
B: Great. We can sing songs and read some funny stories for them. They must feel happy.
A: By the way, what are you doing on May Day? Are you going to (___) World Expo(世博会) 2010 in Shanghai?
B: I will, if I’m (__). But I’m afraid I have to study for the coming tests. It’s (__) for us, you know.
A:OK. Hope you can go with me. See you.