The captain knew that ( )the only attempt a his would not be b it was not c it had not beenThe captain knew that ( )the only attempta his would not be b it was not c it had not been

The captain knew that ( )the only attempt a his would not be b it was not c it had not beenThe captain knew that ( )the only attempta his would not be b it was not c it had not been
The captain knew that ( )the only attempt a his would not be b it was not c it had not been
The captain knew that ( )the only attempt
a his would not be b it was not c it had not been

The captain knew that ( )the only attempt a his would not be b it was not c it had not beenThe captain knew that ( )the only attempta his would not be b it was not c it had not been
his=his attempt 等号前面的his是名词性的物主代词,等号后面的his是形容词性物主代词
选a 表示从句是过去将来时态,从过去的观点将来要发生的事.
整句话的意思是：船长知道,他的努力将不是唯一的（努力）.

b it was not