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1. Lan: Where are you going, Nam?
Nam: I′m going to the amusement center. I′m going to play video games there.
Lan: How often do you go?
Nam: Not often. About once a week.
Lan: Isn′t it  ?
Nam: Not really. I usually stay for about an hour. I don′t spend much.
Lan: You must be careful. Video games can be  . Don′t spend too much of your time in the arcade.
Nam: Don′t worry, I won′t. I have a lot of homework to do tonight, so I can only play games for a   time.