The sentence that state the key idea or main idea of the article is:".Tenayuca worked to improve the lives of Mexican American workers." (Option D)
The idea around which other ideas revolve is called the main or central idea.
It is to be noted that Emma Tenayuca was a Fearless Mexican American labor activist. Because she helped to improve the lives of Mexican American workers, she was nicknamed "La Pasionaria de Texas"
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