Answer: D. every cloud has a silver lining
The cloud represents a dark, scary, or sad moment. This is in contrast to the sun which metaphorically represents energy and happiness. The cloud sometimes covers up the sun to cover up those happy moments so to speak.
Despite the cloud being present, there's a silver lining to the cloud which represents some positive aspect a person didn't expect to happen. In this case, the problem allows Sean to get stronger. So this is an opportunity for his growth.