A:It
B:Thi
C:What
D:A
位于赤道和180°经线上的某舰艇,向正北方向发射炮弹,炮弹应落在( )
①东十二区 ②西十二区 ③180°经线以东 ④西半球.
All the kids had a lot of fun Children's Day. They sang and danced happily all day.
涨潮时,牡蛎将壳张开进行取食,退潮时则将壳紧闭.这种行为属于( )