判断字符型变量ch是否为大写英文字母，应使用表达式

A．ch＞='A' & ch＜='Z'

B．ch＜=\A'‖ch＞='Z'

C．'A'＜=ch＜='Z'

D．ch＞='A' && ch＜='Z'

The agreement indicates that the two companies will ________ with each other again.[ ]

A. team up  

B. turn up

C. look up  

D. pick up