Concept:The word that fills the gap must be the closest opposite of “careless” and make the sentence logical.Explanation:“Careless” means not paying enough attention or acting without caution.“Cautious” means being careful, watchful, and alert to possible danger.Thus, “cautious” is the direct opposite of “careless”.The other options do not express this opposite meaning: “experienced”, “equipped”, and “considerate” are not antonyms of “careless”.Answer:B. cautious