The correct option to ask a six-year old boy if he likes sweets is:
B. ¿Te gustan los dulces?
Explanation:
To ask a six-year old boy if he likes sweets the correct answer is B: Do you like sweets? Option A is incorrect because the use of "nos" implies the question is being made about "us" and that's not the intention. In English it would be "do we like sweets?". Option C is talking about myself: "Do I like sweets?". Option D is directed to another person but is not asking whether he likes sweets or not but instead is just offering them: "Do you wants sweets?"