A:(5,2)
B:(﹣6,3)
C:(﹣4,﹣6)
D:(3,﹣4)
An ant was drinking by a small river when it fell in.It made ______ efforts to reach the side,but made no progress at all.
将下列陈述句改成反问句。
①我是好学生。
②吸毒是不正确的。
关于密度,下面理解正确的有( )