Final answer:
The correct radical expression of a^5/7 is the seventh root of a raised to the fifth power, which is √a^5 with an index of 7. This is represented by option B.
Step-by-step explanation:
The expression a5/7 represents the seventh root of a raised to the fifth power. To express this as a radical expression, we could write it as √a5 with an index of 7, which denotes the seventh root. So, the correct radical expression for a5/7 is option B, which is the √a5 with an index of 7. An alternative way to express it using a rational exponent would be by writing it as (a1/7)5, since rational exponents can be interpreted as roots.