The answer is C. 546.
If a population decreases by 11%, that means that 89% (100% - 11% = 89%) of cheetahs remains each number. 89% can be expressed as 0.89, so to calculate the change of the population, we must each year multiply the number of cheetahs by 0.89.
After 1 year: 1750 * 0.89 ≈ 1558
After 2 years: 1558 * 0.89 ≈ 1387
After 3 years: 1387 * 0.89 ≈ 1234
After 4 years: 1234 * 0.89 ≈ 1098
After 5 years: 1098 * 0.89 ≈ 977
After 6 years: 977 * 0.89 ≈ 870
After 7 years: 870 * 0.89 ≈ 774
After 8 years: 774 * 0.89 ≈ 689
After 9 years: 689 * 0.89 ≈ 613
After 10 years: 613 * 0.89 ≈ 546