序言，是一种实用文体。为自己的书写的序言称为___________。
自序
按要求改写句子。
1. There were many people there. (变为否定句)
There ______________ many people there.
2. I'm going by plane. (就画线部分提问)
______________ are you going?
某工厂工人生产零件数的资料如下：
请根据资料回答下列问题：
第三组的频率是（）。
A.10%
B.12%
C.15%
D.17%
