Which of the following means "an expression designed to call something to mind without mentioning it explicitly; an indirect or
passing reference."

According to the Oxford Dictionary of English, “allusion” as a noun can have the following definitions: An expression designed to call something to mind without mentioning it explicitly; an indirect or passing reference. The practice of making allusions. Passing reference or indirect mention.

Explanation:

the correct answer is:   [c]:

                    →     " leave it out. "  

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        best wishes!

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