为什么He said he must leave early等效转换是He said he would have to leave early?而不是He said he had to leave early为什么这里have to表示将来要用将来时啊,在We have to leave early tomorrow中have to同样是表示将来,却没用will have to
问题描述：
为什么He said he must leave early等效转换是He said he would have to leave early?而不是He said he had to leave early
为什么这里have to表示将来要用将来时啊,在We have to leave early tomorrow中have to同样是表示将来,却没用will have to
答
must 和have to一个是主观意愿，一个事客观意愿。等效转换中，用would have to 不是更委婉吗，语气不是更好吗？
答
因为前面的said是过去时
答
He said he must leave early等效转换是
He【 said 一般过去时】he 【would have to 过去将来时】 leave early
即,过去说他将要做某事.
时态搭配原则：
主句用过去时态,从句只能是过去的某种时态形式【表示客观事实和真理的情况例外】