The teacher said he would fail me if I don't work harder.
这里would是不是用错了,如果按照if从句是一般现在时,主句应该用will。
【答】正确的句子应该是:The teacher said he would fail me if I didn't work harder.
请看句子的演变过程:
直接引语 The teacher said :“I will fail you if you don't work harder.”
间接引语 The teacher said he would fail me if I didn't work harder.