Which Is NOT One of the Worries Scholars and Survey

Which is NOT one of the worries scholars and survey professionals have in terms of undermining the validity of a survey?

A) Americans will not answer calls that ask for personal information due to fears of identity theft.
B) Americans have become less willing to answer pollsters' questions because advertisers have sometimes disguised themselves as researchers.
C) Americans are increasingly using caller ID to screen out unwanted or unsolicited calls.
D) Americans are relying more and more on mobile phones, which are often turned off.
E) Americans are using answering machines to avoid answering unsolicited calls.