下列减弱噪声的措施中，属于在传播过程中减弱噪声的是（）

81的平方根是____； 的算术平方根是____．

找出所给问句的对应答语。

①Can I help you?                                ____                     A. I'd like some oranges.

②What do you need?                          ____                     B. Three.

③How many books do you want?        ____                     C. Yes, I think so.

④Is that all?                                         ____                     D. Yes, I need some milk.

⑤What would you like?                        ____                     E. I need some fish.