Which of the following statements is true of negative advertisements?

a. Negative television advertisements are less likely than positive ads to grab the viewers' attention and make an impression.
b. Negative advertisements are less likely to focus on substantive political issues and thus they do a poorer job of informing the voters about important campaign issues than positive ads do.
c. Negative television advertisements never work.
d. The more negative the television advertisements, the less likely it is to get free media coverage.
e. Presidential candidates typically assert that they use negative advertising because it works.