Believe it or not，my sister and I are twins.—Oh，you must have had the case________you were taken for your sister.

下列各句中，表达得体的一句是

(2013·高考湖南卷)The university estimates that living expenses for international students________around $8,450 a year，which________a burden for some of them.

What do you usually do on your ________— I usually play games and type myhomework.

I wonder how you finished the work.