21．—It's cloudy outside．Please take an umbrella．
— ．
A．Yes，take it easy B．Well，it just depends
C．All right，you're welcome D．OK，just in case
22．—Will you go to Mary's birthday party?
—No， invited，I can't go to it．I'll be too busy then．
A．as if B．unless
C．even though D．when
