三题高一英语,1,Many people agree that ___ knowledge of English is

三题高一英语,
1,Many people agree that ___ knowledge of English is a must in ___ international trade today.
/.请问下为什么
2,All are present and all is going on well.请问为什么第一个是are第二个是is
3,--It was not until I came back that he went to bed.
--It was obvious that he was worried about you.
请问为什么用not until
第二题完整的是All are present and all is going on well.Our monitor said.如果说修饰人就是复数，物就是单数，那么请解释下这句意思赖！

1、A KNOWLEDGE OF加学科是固定的,后面的international trade 是国际性的贸易显然不需要用什么冠词
2、如果ALL修饰的是人就用复数,修饰的是事情,就用单数.
3、固定搭配