Choose a phrase that best describes a person with good judgment.

The correct answer is: Someone who is good at deciding whether something is good or bad.

The correct answer is A-  Someone who is good at deciding whether something is good or bad. as , being a calm /steady/ intelligent person (as mentioned in options B and C) might not always necessarily guaretee them to be a person with good judgement, but someone who can assess good or bad can always make good judgements.