Question

An author describes several important opportunities in her life as “a series of open doors.” What type of literary device is the author using?

A. allusion
B. hyperbole
C. idiom
D. metaphor

Answer 1

The answer is C! The definition of an idiom is an expression in the usage of a language that is peculiar to itself either in having a meaning that cannot be derived from the conjoined meanings of its elements (such as up in the air for "undecided") or in its grammatically atypical use of words (such as give way)

Answer 2

The answer is C idiom
This is because idiom means a group of words established by usage as having a meaning not deducible from those of the individual words (e.g. over the moon, see the light )