The conference will begin in an hour; ________, let's have a rest.
A:on the meantime
B:in the meantimes
C:in the meantime
D:in meanwhile
实验中,需要“加热约5mL(毫升)水至沸腾”,要用到的下列仪器是( )
已知y=kx+b,当x=2时,y=-2; 当x=3时,y=0,则( )
我国人口地理分界线(即人口密度线) ( )