The correct answer is:
c) He was not limited on how much money he could raise.
Public finance contributions for presidential campaigns were used by almost any party until recent years. This means that if a candidate collects $100,000 for the primary, along with at least $5,000 in small contributions from a minimum of 20 states, he becomes eligible for public funds that match the donations received.
However, public funding has a spending limit. As Obama initiated, in the present, most major-party candidates reject public funding because they can raise and spend much more money on their own.