what is the geometric mean of 7 and 12?

a. 1 5/7
b. 9.5
c. 2 √21
d. 4 √21

The geometric mean of two numbers is the square root of their product.

Geometric mean = √(7 * 12) = √84 = 2 √21

Therefore, the correct answer is option c. 2 √21.