难度和区分度之间的关系描述正确的是（）。

If you are interested, we will be pleased to send you a sample lot ______ charge．

A．with B．without C．free D．free of

If you are interested, we will send you a sample lot _____ charge.

A. within

B. with

C. for

D. free of

A．free of

B．within

C．for

D．with

A、Yes, we will send the information you requested.

B、This is to advise you that we will send the information you requested.

C、You may be interested to learn that we will send the information you requested.

D、I am writing this letter to inform you that we will send the information you requested.

We should be pleased to send you a sample ____ our own expense.

A．at

B．in

C．against

D．of

A．appreciated

B．appreciate it

C．appreciate you

D．appreciate

We should be pleased to send you a sample ____ our own expense.

A. at

B. in

C. against

D. of

A．A.on request

B．B.by request

C．C.in request

We are ______ you for the special offer you send us.

A．thank B．appreciate C．grateful for D．indebted to