21．What _____ pity that you couldn’t go there to receive ______ prize!
A．a; a B．the; a C．a; the D．the; the
22．According to the rules of the library, a book can _____ for three weeks, and a DVD for one week.
A．borrow B．kept C．be kept D．be borrowed
23．Generally speaking, according to the directions, _____ the drug has no side effect.
A．when taken B．when taking C．when to take D．when to be taken
24．Mary can speak Chinese fluently, _____ impressed me most.
A．why B．that C．where D．which