Tom's father gave him a valuable gift as an … to make him work harder in school.

Step 1: Analyze the question The sentence says Tom's father gave him a valuable gift "to make him work harder in school." We need a noun that means something given to motivate or encourage someone to act.

Step 2: Explain the concept An incentive is something that motivates or encourages a person to do something, such as a reward promised or given to boost effort. The phrase "an incentive to + verb" is a common collocation.

Step 3: Test each option

• A. incentive: It fits perfectly. A gift given to push Tom to work harder is an incentive.
• B. attraction: This means something that draws interest or appeal, like a tourist attraction. It doesn't suit the idea of motivation to study.
• C. interest: This is a feeling of curiosity or concern. A gift is not "an interest to make him work harder."
• D. offer: This is something proposed for acceptance. It is not usually followed by "to make him work harder," and it doesn't carry the idea of motivation.

Step 4: Answer The best word is incentive, so the answer is A.

Tip: When a sentence talks about something given or promised to make someone do better or act, think incentive, motivation, or reward. Remember: incentive = in + centre of motivation, something that "sets you going."