Which is true about letters to the editor?
they are a type of informal correspondence.
they are an opportunity to present viewpoints on important issues.
they are written by people who want to get work as editors.
like newspaper articles, they feature facts, not opinions.

The correct answer is They are an opportunity to present viewpoints on important issues.

Explanation:

A letter to the editor is a type of letter written in response to a publication usually from a newspaper or magazine, in which the reader's point of view on an important problem is expressed.

It is expected that these types of letters will be published, therefore you should avoid using informal language.

Its main themes may be to support or oppose any publication made by an editor, or comment on an important issue that is occurring, among others.

be more specific with your question.