Antonym of GRIM

serious
satisfying
delightful
painful

The correct answer is: B. satisfying

A grim expression is one that is serious, stern, or forbidding. A satisfying expression is one that shows pleasure or contentment.

The other options are not antonyms of grim.

A serious expression is one that shows concern or importance. A delightful expression is one that shows pleasure or enjoyment. A painful expression is one that shows discomfort or suffering.