Dark clouds are a ________ of rain while a smile is a ________ of friendship.

1. A.
   gesture, sign
2. B.
   sign, gestures
3. C.
   sign, gesture
4. D.
   sign, sign

Dark clouds are a ________ of rain while a smile is a ________ of friendship.

[　　]

A．gesture, sign

B．sign, gestures

C．sign, gesture

D．sign, sign

Dark clouds are a ________ of rain while a smile is a ________ of friendship.

[　　]

A．gesture, sign

B．sign, gestures

C．sign, gesture

D．sign, sign