4个简单选择```````问题严重.....急

CThat was why ...这是我悲伤的原因,why 引导 表语从句
B how to do it，表方式，如何...

B fell;was riding 正在骑车时摔了下来
C or 否则的话

We didn't know ____ to do it.
A what
B how
C which
D why
宾语从句。我们不知道...。纯粹从意思上考虑。

What happened to Mary's brother?
He ____ off while he ___ a bike.
A ws falling;rode
B fell;was riding
C falls;is riding
D was falling;was riding
while表同时，所以都是进行时。

Hurry up,____ you'll be late for school
A but
B and
C or
D so
不然你就会迟到。从意思上考虑。

I lost my purse on the way home,That was ____ I looked sad.
A because
B so
C why
D how
宾语从句，排除B，宾语从句不能用so。
从意思排除D。
从句为“I lost my purse on the way home”，选C。
“这就是为什么我看起来很伤心。”
与“I looked sad because I lost my purse on the way home.”区分

1，WHY 表示原因，THAT 是原因，后面是结果。
2，DO后面要加宾语，现在已经有宾语IT 了，所以用HOW，表示如何去做，HOW提问的是副词，状语部分。
3，FALL是瞬间动作，不能用ING，那表示正在掉下来