---Tell us, Mark, what is the cause of the American Civil War?
---Well, is it _______the black slaves wanted freedom?
A． how B． why
C． because D． when
--- I can’t carry the luggage．It’s so heavy.
--- Why not have someone strong enough_______ you a hand then?
A． give B． to give
C． giving D． to have given
Although she brushed the old pot_______, she could not make it completely clean, which made her very upset.
A． roughly B． thoroughly
C． instantly D． occasionally
Mr．Smith is always on time for everything．How ____ it be that he was late for the important meeting?
A． should B． can C． may D． must
---Your grandfather still seems very energetic, although he is already in his seventies now.
---Yes, he _______in the army for three years when he was young.
A． would serve B． served
C． had served D． has served
Many plants could move northward and toward the Pacific coast _______rising temperatures and changes in rainfall.
A． for fear of B． in defense of
C． by means of D． in reaction to
