三叉神经痛最有效的首选药物是（）.

A.苯妥英钠

B.卡马西平

C.氯硝西泮

D.维生素B₁₂

E.巴氯芬

The achievements of the greatest minds in science could never have been reached if it had not been for the patient and accurate work of hundreds of other people.

A．has it not been

B．if it had been

C．if hasn't been

D．had it not been