His disposition towards labour made him endearing to the Manager.

The correct answer is A. inclination.

Inclination means a natural tendency or preference towards something. In this case, the Manager was fond of the employee because the employee had a natural tendency to work hard.

B. unwillingness means a lack of desire or willingness to do something. This is not the correct answer because the employee

C. temperament means a person’s characteristic emotional nature or mood. This is not the correct answer because the employee’s emotional nature or mood was not mentioned in the question.

D. watchfulness means the act of keeping careful and continuous observation over something. This is not the correct answer because the employee was not mentioned to be keeping careful and continuous observation over something.