A:X的原子序数比Y要小
B:X的原子最外层电子数比Y大
C:X的原子半径比Y的小
D:X元素的最高正价比Y小
Tony knows China very well because he ______ in China for twenty years.
假如从天津乘船到海南岛的海口市,依次经过的海洋是( )