A：扩大2倍
B：不变
C：缩小2倍
D：扩大4倍
已知圆C和y轴相切，圆心在直线x﹣3y=0上，且被直线y=x截得的弦长为27，求圆C的方程．
根据问句找出相应的答句
____ What can you do? A. She can do some kung fu.
____ What can she do? B. Fish.
____ Can you use a computer? C. No, I can't.
____ Can you speak English? D. Yes, I can.
____ What's your favourite food? E. I can play the erhu.
“物质的量”的符号是（ ）
