A person who uses investigations and journalism to expose a problem to the public is known as

Most of these journalists called themselves called muckrakers.

Explanation: The term muckraker (MUK + RAY + KUH) eventually came to be used in reference to investigative journalists who reported about and exposed such issues as crime, fraud, waste, public health and safety, graft, illegal financial practices.

The muckrakers were reform-minded journalists in the Progressive Era in the United States who exposed established institutions and leaders as corrupt. They typically had large audiences in popular magazines.

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