Well, since C is the only example where a positive thing happens, then it is certainly not a potential problem, so 'they can provide a lot of energy for people to use' is the correct answer. The other examples are problematic.
Answer:
A
Explanation:
spent is in past tense form of the verb. hence, choose the question tag in the same tense i.e., past tense.
Answer:
Having Leader, Social Relationship and Norms
Explanation:
