The rational exponent that represents a square root is option A, 1/2.
In general, if we have a number x and we raise it to a rational exponent of the form p/q, where p and q are integers and q is an odd integer, then we can find the qth root of x raised to the pth power.
For example, if we have x = 4 and we raise it to the exponent 2/3, then we can find the cube root of 4 squared, which is the same as the cube root of 16.
However, if we take x = 16 and raise it to the exponent 1/2, then we can find the square root of 16, which is 4.
Therefore, the rational exponent that represents a square root is 1/2.