性发育(sexdevelopment)
参考答案：
青春期的重要表现，包括生殖器官形态、生殖功能和第二性征发育。
To learn English well, we should find opportunities to hear English _____ as much as we can .[ ]
A. speak
B. speaking
C. spoken
D. to speak
安全标志分为（）。
A.禁止标识
B.警告标识
C.指令标识
D.提示标识
