XBL须在哪里定义？（）
A.RXCDR
B.BSC
C.BTS
D.RXCDR和BSC都要定义
参考答案：D
简述补强剂的作用。
Why not an English language club to practice _____ English.
A．join, speaking
B．to join, speak
C．joining, speaking
D．take part in, speaking
