--- Jack fell off the ladder yesterday, but he is all right now.
---What a lucky dog! He _______ himself badly.
A． could injure B． must have injured
C． should injure D． might have injured
---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
