199+299+399+…+29699,
=1+2+3+…29699,
=148×29799,
=444.
找出错误并改正。
( ) 1. Where do you sending your letter? _____________
A B C
( ) 2. I'm writeing a letter to my mother. _____________
常年运行的压缩机则()年更换一次冷冻机油。