The driver would have been in trouble if he’d drunk that night.这里的if he'd drunk that night.是he would drunk还是he had drunk.

问题描述:

The driver would have been in trouble if he’d drunk that night.
这里的if he'd drunk that night.是he would drunk还是he had drunk.

是he had drunk.
虚拟语气,用过去完成时表示一般过去时