Work that does not engage a person will never seem rewarding, no matter how lucrative it becomes.

Answer: Option D

Promising : showing signs of future success.
Easy : achieved without great effort; presenting few difficulties.
Comfortable : (especially of clothes or furnishings) providing physical ease and relaxation.
Profitable : (of a business or activity) yielding profit or financial gain.
Lucrative : producing a great deal of profit.

Synonym of Lucrative is Profitable