it known to all和as is known to all有什么区别?______is known to all,goo_英语解答

it known to all和as is known to all有什么区别?
______is known to all,good friends add hapiness and value to life.
答案说是填as,为什么不能填it呢?两者有什么区别

人气：489 ℃　时间：2020-03-23 01:19:38

解答

因为填it的话就会有两个主句,前面一句,后面一句,这是不符合语法的.填As的话前面一句就是从句,就可以.单独用都没错