若 |a+6|=0 ,则a=____;若 |a|=-a ,则a____0.
The shopping mall _____ very early and it _____ after 10:00 p.m.
物质在不同条件下的三态变化,主要是由于构成物质的微粒( )
下列既是海港又是河港的城市为
____ ____ ____ ____ Watch?