有一个由A、B和C组成的三人社会，个人对公共产品的需求函数分别为PA=100-3q，PB=200-4q，PC=400-10q。如果该公共

—Has Maria arrived yet？—No, she ______ an hour ago.

A．was supposed to come

B．ought to have come

C．should come

D．must have come

They ____________(一定是误了火车), otherwise they should have arrived here two hours ago.

___________ (Cathy一定是误了火车). She should have arrived here two hours ago.

The train arrived one hour behind().

A、plan

B、timetable

C、schedule

D、date

A．should have arrived

B．need arrive

C．must have arrived

D．may arrive

听力原文：M: It's 8: 20 . The train should have arrived at 8:00.

W: Yes. Something must be wrong on the line.

Q: How many minutes was the train late？

(14)

A．10 minutes.

B．A quarter.

C．20 minutes.

D．Half an hour.

A．should have arrived

B．need arrive

C．must have arrived

D．may arrive

听力原文：W: Jack, Where have you been？ You're supposed to get here an hour earlier.

M: Sorry, Aunt Ruth, but I'm afraid I don't know my way around Manchester yet.

Q: What can we learn about Jack from this conversation？

(17)

A．Jack is new in Manchester.

B．Jack was in a traffic jam just now.

C．Jack arrived an hour earlier.

D．Jack went to Manchester an hour ago.