didn't know you were so busy.为什么这个句子里有两个过去时?不是每个句子里只能有一个吗?

Hello!I didn’t know you were here. they even didn't know who you were.how______they___(believe) I didn't know you were so busy. Sorry I [didnt] know you were sick.括号中为什么用didnt. I didn't know you were in China .中开头那为什么用didn't啊? 请问：I didn't know it were you.为什么一定要用were呢? i didn't know you were sleeping为什么要用were 英语翻译I didn‘t know you were coming,so I didn’t buy any beer.(If…虚拟) Glad to meet you .I ____you were here.A.don't know B.won't know C.didn't know C.haven't know Honey,I didn't know that you were so much concerned with the world development. I didn't know you were so busy.变被动语态 l didn't know you were so busy ,这里怎么有两个过去式? Didn't you know that your parents were worried about you为什么用were不能用原形?Didn't对that从句的时态没有限制作用? What a surprise!　　I＿＿＿you＿＿＿here　in　Wuxi． A,didn＇t　know　,were　　B,didn＇t　know　,are I didn't know you were so busy一般疑问句I didn't know you were so busy 一般疑问句我想的是Did you know me was so busy?错了么 I didn't know you were in New York .how long__here A have you B were you C have you beenD will you come I would have come sooner but I _________ that you were waiting.A didnt know B dont know C hadnt known D havent known oh,it's you.i'm sorry i ____ know you _____ here.A.didn't are B.didn't were