日常食用的“茧蛹”实际上是柞蚕的蛹，由此判断柞蚕的发育过程经过[ ]
A．两个时期
B．三个时期
C．四个时期
D．五个时期
答案：C
If an "internet friend" asked you to meet, you would ______. [ ]
A. go alone
B. meet in a tea bar
C. let your parents know it
D. do behind your parents.
极化天线的优缺点及原因有哪些？
