Bettina is a property investment manager who wants to write to a client telling him that the new sprinkler system installed at his property has already reduced its water bill by hundreds of dollars over last year. Which of the following guidelines should Bettina follow when writing this message?

A. She should include all necessary explanations in the body of the message.
B. She should end with a general closing, such as "If you need further information, just ask."
C. She should write the message using the indirect approach of organizing information.
D. She should explain the orienting material in detail and keep the main objective brief.
E. She should present the objective or key point of the message at the end.