世界降水最少的“干极”出现在( )
A:阿塔卡玛沙漠
B:南极大陆
C:塔克拉玛干沙漠
D:撒哈拉沙漠
地球在公转时,地轴是____ 现象,而且它的____ 保持不变。
读某地区等高线地形图,完成下列问题。
I've asked him __________ us for dinner, but he said he was quite busy.