The correct answer is **to waste one's efforts** (Option 1). **Comprehensive Derivation:** The correct answer is - "to waste one's efforts". Explanation & Key Takeaways: • From the given options, the most appropriate answer is "to waste one's efforts". • To flog a dead horse means waste energy on a lost cause or a situation that cannot be changed.. • Eg. It is useless to flog a dead horse. • Here sentence B says that speaker heard that insurance advisor is wasting his efforts on the so-called prospect for the seventh time. • Thus, Option 1 is correct option. **Option Elimination:** • **Option 1 (to waste one's efforts)**: Correct Answer; accurate according to canonical reference. • **Option 2 (to waste one's money)**: Incorrect distractor. • **Option 3 (to kill someone)**: Incorrect distractor. • **Option 4 (to waste one's time)**: Incorrect distractor. **Exam Trap:** Be careful of misleading distractors and subtle terminology differences. Verify core properties before selecting your answer. **Memory Booster:** Core mnemonic rule: to waste one's efforts corresponds to Option (1).