didn't know,had't know和haven 't know用法有什么区别

didn't know,had't know和haven 't know用法有什么区别 两个简单的英语语法问题,I don't know和I didn't know有什么区别额? I didn’t know He didn't know ( i don t know和I didn't know的区别 didn't和haven't什么有区别 请问 I didn't know和little did i know的区别 I didn't know与I know nothing有什么差别 I didn't pretend to know him 和 I pretended not to know him 有 i wouldn't know 和 i don't know 有什么区别呢?只是委婉一点吗? l don't know 与l didn't know的区别 haven't和 didn't的区别