He is rather difficult to make friends with，but the friendship of his，once ________, is more true than any other．

1. A.
   gained
2. B.
   to gain
3. C.
   having gained
4. D.
   gain

He is rather difficult to make friends with，but the friendship of his，________，is more true than any others'.

A．once gained　　 　　 B．when to gain

C．as gained　　 　 D．while gaining

He is rather difficult to make friends with， but the friendship of his，______ ，is truer than any other．

A．once gained　 B．when to gain　　 C．after gained 　 D．while gaining

He is rather difficult to make friends with，but the friendship of his，once ________, is more true than any other．

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He is rather difficult to make friends with，but the friendship of his，once ________, is more true than any other．

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