Which of the Following Statements Is True About Sales Promotion

Which of the following statements is true about sales promotion?

A) It is the cheapest method of personal communication.
B) It is more flexible than personal selling.
C) It offers incentives to customers to purchase products during a specific period.
D) It restricts a firm from controlling the content and exact delivery of its marketing message.
E) It is more reliable than the word-of-mouth method of marketing communication.