我国下列省行政单位中,既有陆上国界线,又有海岸线,同时还有阳光直射现象的是( )
A:桂
B:粤
C:滇
D:辽
若n为正整数,且x2n=3,则(3x3n)2的值为____.
When I as well as my cousins __________ as a volunteer in Beijing, I saw the Water Cube twice.
如果a=b,则下列式子不成立的是( )
读黄河流域图,回答下列各题。