—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

X线平片肾结石不显影的是（）

A.磷酸钙结石

B.草酸钙结石

C.尿酸盐结石

D.磷酸镁胺结石

E.胱氨酸结石