Final answer:
The opposite of 'laborious' is 'relaxing', since laborious activities require a lot of effort, while relaxing ones do not.
Step-by-step explanation:
The opposite of the capitalized word LABORIOUS is 'relaxing' (option A). A laborious activity is one that is very hard and demands a lot of effort and work. Therefore, the opposite would be an activity that is easy-going and not demanding, which is well-represented by the term 'relaxing'. In contrast, the other options such as strenuous, arduous, and burdensome are synonyms of laborious, and boring does not accurately represent the antonym we are searching for in the context of effort and difficulty.