If Tom had spent more time studying, he       able to do well in the test now.

A．will be

B．would be

C．has been

D．would have been

母牛在分娩过程中体力消耗很大，因而分娩后的母牛应立即喂给足量的精饲料，以促进体力恢复和胎衣的排出。