Question

complete the sentence with the best correlative conjunctions.
the international astronomical union has established criteria that help astronomers as they determine __ planet __ dwarf planet is the correct classification for a given celestial body.
if... then
whether... or
neither... nor

Explanation:

The sentence is about determining the classification of a celestial body as either a planet or a dwarf planet. The correlative conjunction "whether...or" is used to present two alternative options for classification, which fits the context. "if...then" is used for conditional statements, and "neither...nor" is used to negate both options, which don't fit here.

Answer:

whether...or