Dear Mr. Smith:
Thank you very much for your inquiry dated December 12, 2002.
I am glad to tell you that we are an outstanding hi-tech company specializing in telephone facilities and are able to offer you our exclusive products (独家产品) , Pentium telephone recorders, at a very reasonable price. A 15 per cent further discount is usually offered for an order for 300 units or more.
The recorder can be placed virtually anywhere or even so far from the telephone set that the coming speaker is unaware of its presence. It is completely automatic, started and stopped by electronic controls. Its direct contact with the telephone wire ensures highest fidelity (高保真) recording. The recording volume level is automatically maintained with its built-in ability to boost it when low or to cut it down when high, which is particularly useful in recording long distance calls.
This is an unusual opportunity for you to get an unusual product. I am looking forward to receiving your initial order as soon as possible.
Yours sincerely,
Paul Y. Shen
General Manager
ABC CompanyThe word "boost" (Line 5, Para. 3) probably means （）

A．to cut
B．to lower
C．to keep
D．to increase