Democratic presidential frontrunner Hillary Clinton told NBC's Meet the Press on Sunday she feels "sorry" for Sen. Bernie Sanders' (I., Vt.) young supporters who are not getting all of the facts about her campaign.

Clinton told host Chuck Todd that she is used to criticism and has been taking it for close to two decades. Clinton touted her efforts during her time as a senator from New York to get away from fossil fuels and rely more on clean energy.

"When I was Secretary of State, I was at the original meeting in 2009 with President Obama where we were trying to convince China and India and others to come on board with accepting some restrictions that would lead to what finally occurred with a Paris agreement," Clinton said.

On Thursday, a Greenpeace activist asked Clinton if she would stop taking money from the fossil fuel industry as well as their registered lobbyists. She snapped at the activist that she only accepted money from people who work for the fossil fuel industry. She added she was "so sick" of the Sanders campaign lying about her.

"I feel sorry sometimes for the young people who believe this," Clinton said. "They don't do their own research, and I'm glad that we now can point to reliable independent analysis to say, no, that's just not true."

Clinton used analysis from the Washington Post and the New York Times to prove that the Sanders campaign has been incorrect about her record. She has been trying to make the case for young people, especially young women, to vote for her since the beginning of her campaign. Younger voters view her as untrustworthy and do not feel that she is as transparent as Sanders.

In a March Washington Post-ABC News poll, only 37 percent of respondents believe that Clinton is trustworthy while 57 percent do not believe that she is.

Sanders has a four-point lead in a recent poll of Wisconsin, whose primary is Tuesday.