Viral Marketing Proved to Be an Effective Tactic ________

Viral marketing proved to be an effective tactic ________.

A) following the SARS outbreak in Canada in 2003
B) with the introduction of the personal computer in 1977
C) that led to the election of Bill Clinton as U.S.president in 1992
D) with the introduction of Microsoft's Vista operating system in 2005
E) that helped the Allies counter Nazi propaganda in World War II