Final answer:
The line is an example of a paradox, a statement that seems contradictory but actually reveals a truth. It differs from an oxymoron, metaphor, and allusion, none of which are represented in this example.
Step-by-step explanation:
The line "Imaginatively she is of the highest importance; practically she is completely insignificant" is an example of paradox. A paradox is a statement that may seem contradictory but can reveal a truth upon further examination. It expresses two opposite ideas that together deliver a singular, thought-provoking concept. Unlike an oxymoron, which brings together two contradictory terms in close conjunction, or a metaphor, which is a direct comparison of two unlike things, a paradox involves a fuller statement or a complete sentence that presents contradictory elements. An allusion refers to a brief and indirect reference to a person, place, thing, or idea of historical, cultural, literary, or political significance. The given line does not make such a reference, therefore, it is not an allusion.