7221. We must not take his facetious remark very seriously.

✅ The correct answer is option D.
Amusing : causing laughter and providing entertainment.

Critical : expressing adverse or disapproving comments or judgements.

Casual : relaxed and unconcerned.

Flippantly : not showing a serious or respectful attitude.

Facetious : treating serious issues with deliberately inappropriate humour; flippant.

Synonym of Facetious is Flippant