About once per test, an SAT Error ID question will leave the ‘ly’ off the end of an adverb. An adverb is a word, usually ending in ‘ly’ (like ‘clearly’, ‘mostly’ or ‘faithfully’), that helps describe (or modify) an adjective, a verb, or another adverb.
Researchers examined the constant changing river bed for signs of invasive species.
Problem: The adverb ‘constant’ is missing ‘ly’.
(The river bed can not both be ‘constant’ and ‘changing’ at the same time.)
Researchers examined the constantly changing river bed for signs of invasive species.
Tip: The phrase ‘constant changing’ is an SAT favorite when testing adverbs.