Which of the Following Statements BEST Explains Why Incumbents in Congress

Which of the following statements BEST explains why incumbents in Congress have an easier time attracting campaign contributions than challengers?

A) Interest-group contributors believe that their contributions ensure access to members after the election because they are more likely to win.
B) Incumbents are more knowledgeable about how to raise large amounts of money.
C) Incumbents are usually better candidates than those who challenge them.
D) Contributors know where incumbents stand on the issues due to their past voting in Congress.
E) Incumbents are better educated and better connected.