What is the square root of 64?

The square root of a number is the value that, when multiplied by itself, gives the original number. For the number 64, we can determine its square root by finding a number that, when squared, equals 64.

Starting with 8:

8 multiplied by 8 equals 64 (8 x 8 = 64).

Therefore, the square root of 64 is indeed 8. This means that choice C is the correct answer because it satisfies the condition of being a perfect square. The other options do not result in 64 when squared: 6 squared equals 36, 7 squared equals 49, and 9 squared equals 81. Thus, 8 is the only number that fits the criteria for this particular square root.