How would a secondary source be beneficial to a historian studying a particular event?

One of the most important reasons why a historian might benefit from a secondary source when studying a particular event is because the use of a secondary source allows the historian to avoid the need to look back at the primary source. This is because an expert has already studied it, and published it, so that other historians can rely on it. In this way, a lot of money and effort can be saved.

d) a constitutional amendment

question:  

the chart compares religious beliefs to us political party support.

religious beliefs and party support, 2012

this chart demonstrates that

a) more highly religious people supported the republican candidate, while more nonreligious people supported the democratic candidate.

b) more highly religious people supported the democratic candidate, while more nonreligious people supported the republican candidate.

c) more moderately religious people supported the republican candidate, while more nonreligious people supported the democratic candidate.

d) more moderately religious people supported the democratic candidate, while more nonreligious people supported the republican candidate.

answer: a.