He is rather difficult to make friends w
问题:
He is rather difficult to make friends with, but his friendship, _____, is more true than any other.
A.once gained
B.when to gain
C.after gaining
D.while gaining
He is rather difficult to make friends with, but his friendship, _____, is more true than any other.
A.once gained
B.when to gain
C.after gaining
D.while gaining