Labour: work, especially physical work.
Amuse: cause (someone) to find something funny.
Rest: cease work or movement in order to relax, sleep, or recover strength.
Strive: make great efforts to achieve or obtain something.
Thus, option C is the correct answer.
Edit: Based on the input from Aayush Nigam, correct option choice C has been changed from 'CAT' to 'Strive'.