adj.
VERBS
▪ be
▪ become
▪ remain
ADVERB
▪ extremely , fairly , very , etc.
▪ highly
▪
Their motives for undertaking this study are highly ~.
▪ ethically , morally
Questionable is used with these nouns: ↑ assumption , ↑ decision , ↑ legality , ↑ merit , ↑ motive , ↑ practice , ↑ relevance , ↑ reputation , ↑ taste , ↑ validity