From the 1983 British Election Data, Which of the Following

From the 1983 British election data, which of the following is an example of an environmental effect on voting?

A) Differences in local and regional political culture produce spatial variations in the support given to the various political parties.
B) Individuals may be influenced in their voting decisions by their social contacts.
C) Vote-switching is more common in the safer seats and the longer-established parties do better in the marginal constituencies.
D) The higher the level of unemployment in an area, the more successful the Labour Party candidate.
E) None of the above