Final answer:
The best support for getting better at difficult things is part C from the text, as it underlines the significance of managing emotional health as part of the process.
Step-by-step explanation:
The section from the text that best supports the answer to Part A about getting better at difficult things is: C "To 'have it, I must manage my emotional health. Part of that long-term management - beyond French - is giving myself an opportunity to get better at difficult things." (Paragraph 5). This statement emphasizes the importance of emotional health in the process of improving at challenging tasks, highlighting that it's not just about the specific skill (like learning French) but also about the broader goal of self-improvement and resilience in the face of difficulty.