The key point in this question is recognizing the term for a decrease in net income over the previous year. Option C, 'Year-over-year decline', is the correct term used to describe this situation. Option A, 'Revenue growth', indicates an increase in revenue, not a decline in net income. Option B, 'Net loss', refers to a situation where expenses exceed revenue, not a comparison to the previous year. Option D, 'Operating costs', refers to the expenses of running a business, not the change in net income.