Which of the Following, If True, Would Most Weaken an Argument

Multiple Choice

Which of the following, if True, would most weaken an argument for using e-mail for direct mail marketing?

A) Growth in the use of e-mail for direct marketing is uncertain.
B) Studies show that a large percentage of such e-mails go directly to customers' spam folders.
C) Riverdale has traditionally used catalogs for its direct marketing efforts.
D) Not everyone who has used this medium for direct marketing has been successful.
E) Only interested customers will go through such messages in great detail.