invite Tom and Sally to the party tonight？
Good idea．I'll give them a call right now．（ ）
A．WhyB．Why notC．What about
Helen was very rude to me．I refuse to speak to her again __________ she says sorry．（ ）
A．untilB．ifC．becauseD．since
Every time Tom is late， he'll ___________ an excuse． So I wonder what his excuse is this time．（ ）
A．set upB．put upC．take upD．make up
The ____________that there is life on other planets has always encouraged scientists to explore the outer space．（ ）
A．invitationB．possibility
C．orderD．advice
I didn't see you at Jim's party last week．
I had to work that evening， so I _________ go．（ ）
A．needn'tB．mustn'tC．couldn'tD．shouldn't
The path was covered with snow，so we walked very _______．We were afraid of falling．（ ）
A．quicklyB．carefullyC．excitedlyD．hurriedly