The correct answer is C. earn enough.
To make both ends meet means to have enough money to cover all of your expenses. If someone cannot make both ends meet, it means that they are not earning enough money to cover their expenses.
Option A, manage the business, is incorrect because it is not about earning money. It is about running a business.
Option B, work hard, is incorrect because it is not about how much someone works. It is about how much money they earn.
Option D, control affairs, is incorrect because it is not about money. It is about having control over one’s life.