“指南针”现象说明了什么？
参考答案：
最早由中国人发明的“指南针”，说明了地球存在着一个大磁场。
Jack has gone to Australia, but I'm wondering why he ______ in such a hurry.[ ]
A. left
B. has left
C. leaves
D. was leaving
简述小麦印度腥黑穗病分布情况。
