3. Progressive Era writers such as Upton Sinclair were known as "muckrakers" because they Engaged in "yellow journalism that had a negative effect on U.S. foreign policy Defended the interests of agricultural workers against those of the urban workers Exposed serious economic and social problems to public view Inflamed popular feelings against recent immigrants

## Step 1<br />The term "muckrakers" was used to describe journalists and writers during the Progressive Era, such as Upton Sinclair, who were known for their investigative journalism. They were called "muckrakers" because they "raked up" and exposed the "muck" or corruption, social injustices, and economic problems in society.<br />## Step 2<br />These writers and journalists were not known for engaging in "yellow journalism" that had a negative effect on U.S. foreign policy. Yellow journalism refers to a type of journalism that presents little or no legitimate well-researched news and instead uses eye-catching headlines for increased sales.<br />## Step 3<br />They did not defend the interests of agricultural workers against those of the urban workers. Their focus was on exposing the problems in society, not on defending the interests of specific groups of workers.<br />## Step 4<br />They did not inflame popular feelings against recent immigrants. Their focus was on exposing the problems in society, not on inflaming feelings against specific groups of people.<br />## Step 5<br />Therefore, the correct answer is that they exposed serious economic and social problems to public view.