Two differences: Phrase construction: "in most hospitals" "in the majority of hospitals" Countable nouns: "majority" requires a countable noun (e.g. "majority of shoes") "most" is always used for non-countable nouns (e.g. "most information") In informal English, "most" is often used for both countable and non-countable nouns.

D.the majority most --- adverb majority -- noun