--Will you please show me how to operate the new machine?

--Sure. It's a piece of cake. Now let me tell you __________ to do first.

1. A.
   what
2. B.
   how
3. C.
   whether
4. D.
   which

--Will you please show me how to operate the new machine?

--Sure. It's a piece of cake. Now let me tell you          to do it first.

A. what      B. how       C. whether        D. which

[　　]

---Will you please show me how to operate the new machine?

　 ---Sure. It’s a piece of cake. Now let me tell you _____ to do first.