20．The river, ________ banks are covered with trees, is beautiful and it attracts many water birds.
| A．whose | B．what | C．of which | D．which of |
Thebushadleft,sowe_____walkhome.
| A．haveto | B．ought | C．hadto | D．must |
Thedoorisstillclosed.He_____thekey.
| A．musthavelost | B．mustlose | C．needhavelost | D．canlost |
Mary_____beinLondonbecauseIsawherintownjustnow.
| A．mustn’t | B．isn’tableto | C．maynot | D．cannot |
Whenhewasold,MrSmith_____sitforhourswithoutsayinganything.
| A．would | B．should | C．must | D．will |
Iwanttogotothehospital,butyou_____withme.
| A．needtonottogo | B．donotneedgo | C．neednotgo | D．needgonot |