"What was the teacher like?" "If only I could know her."

为什么要把could know 改成 could have known 为什么不改成
had known 这句话什么意思？

"what was the wrong?""what was the matter?""what was trouble?''what happened?'的区别？？？ what's meaning with " That was then ". 请问下面是什么意思“What was the front door like before the salesman came?" "It was locked." what was he doing? What was he drawing______ what was the date? What was Linguistics? "I asked him what he was doing" 这句话的句子结构怎么分析？“what he was doing"在这是什么成分？ what was the industrial revolution ? what was otherwise 怎么解释？？