D中 would have been是将来完成式,不是虚拟语气,已经SUNK了为何要用将来时.是虚拟但时态不对.选C的话逻辑意思变成了“船长应该更小心,他的船就不会沉了.”试问有这么表达的吗.选A的话虚拟是虚拟了,但WERE表达的是尚未实现或者不可能实现的SUNK,问题是已经SUNK了.选B,时态对了,有HAD BEEN MORE CAREFUL,语态也对了,意思过去如果更加小心,穿就不会沉了,逻辑没问题.
找了这两个句子为例：
If the patient hadn't been cured of his disease,he wouldn't be able to go to work.
If the doctors hadn't controlled the disease,the virus would have spread farther.
Had the patient not been cured of his disease,he wouldn't be able to go to work.
Had the doctors not controlled the disease,the virus would have spread farther.