---Look at those shoes, Mike!

---Wow! They look very cool, but I wonder ________.

A．how much are they

B．how much do they cost

C．if my parents will buy them for me

D．that my parents will buy them for me

选出下 * * 种材料中最易切削的两种材料（）。

A.不锈钢

B.45钢

C.铜合金

D.铸铁

E.铝合金