Which of the following is a key difference between House and Senate races?

Which of the following is a key difference between House and Senate races?
 
  a. Overall spending on Senate races surpasses overall spending on House races.
  b. Super PACs are more involved in House races than in Senate races.
  c. House elections are more seriously contested than Senate elections.
  d. Senate elections are more seriously contested than House elections.

Question -2-

The fact that some states have moved their primaries earlier in the election year suggests that __________.
 
  a. they don't believe that caucuses should have as much impact as primaries
  b. they want to have a real impact on the selection of the candidate
  c. they have no fear of the Democratic or Republican National Committee
  d. all primaries should take place on the same day