calling into question vs demand for explanation

calling into question and demand for explanation both are nouns.

Word	Noun	Adjective	Verb	Adverb
calling into question	Yes	No	No	No
demand for explanation	Yes	No	No	No

As nouns, calling into question and demand for explanation are synonyms defined as:

calling into question and demand for explanation: a challenge to defend what someone has said

calling into question (noun)	demand for explanation (noun)
a challenge to defend what someone has said	a challenge to defend what someone has said