划分有无直射阳光的纬度界线是（），划分有无极昼极夜现象的纬度界线是（）。
参考答案：回归线；极圈
用play或play the完成句子。
1. Jenny can _______ volleyball, and she can _______ violin.
2. Jet can _______ trumpet, and he can _______ basketball.
3. Mary can _______ piano, but she can't _______ guitar.
4. Bob can _______ ping-pong, but he can't _______ computer games.
5. Tony can _______ chess, and he can _______ baseball.
平流雾通常产生在（）
A.气温最低的清晨
B.阴天有层云时
C.黄昏气温下降时
D.一日中任何时刻
