【单选题】
24.Don’t worry about Susan. She hasn’t been _____________ she pretends.
【单选题】
If it _____ for his help, I wouldn’t be a university student now.
【单选题】
Why don’t you travel to New York on vacation?
②
Excuse me, because I can’t
③
I want to, but I haven’t got enough money
④
Because I’m going to school today
【单选题】
扭摆仪上只有圆盘时,其摆动周期为T1,放上待测物体后,摆动周期为T2,则()
【简答题】
求圆柱螺线x=cost,y=sint,z=t在t=0处的密切平面