By the time I reached home , my parents ____ the dinner for me already
A:had cooked
B:cooked
C:have cooked
D:cook
PM2.5是指大气中直径小于或等于2.5×10﹣3毫米的颗粒物,也称为可入肺颗粒物,把2.5×10﹣3用小数形式表示正确的是( )
党的基本路线的核心内容是( )