菜刀在生活中有重要应用。下列情况中,菜刀腐蚀由快到慢的是①切青菜后用清水冲洗 ②切湿咸菜后未清洗 ③切肥猪肉后放置
A:①③②
B:②①③
C:③①②
D:③②①
阅读下面的宋诗,完成小题。
山雨
翁卷
一夜满林星月白,亦无云气亦无雷。
平明忽见溪流急,知是他山落雨来。
Yesterday, I visited a middle school in Taiyuan. There are about students in it.
.等差数列{an}满足a2=12,an=-20,d=-2则n=( )