Which of the following would be the most effective closing statement in a routine action request letter？（）

A.Please send a contract for heating and ventilation work by April 1 to allow installation to begin by April 15.

B.Thanking you in advance for sending a copy of the contract for installation of a new HVAC system by April 1.

C.We hope you can get our work completed in a timely manner.

D.I would appreciate receiving a copy of the contract for your proposed installation at your earliest possible convenience.

正确答案：Please send a contract for heating and ventilation work by April 1 to allow installation to begin by April 15.