— I have tried very hard to find a solution to the problem, but in vain.    

— Why not consult with Frank? You see, ______     [ ]

A. great minds think alike      

B. two heads are better than one      

C. a bird in the hand is worth two in the bush      

D. it's better to think twice before doing something

飞机上的紧急出口舱门什么时候可以打开（）。

A.飞机中太热时可开此门

B.在万分紧急和机长的命令下开此门

C.座在舱门旁的乘客可以随意打开此门