7..........:.........

Answer:
option B
4 a^4 /b
Step-by-step explanation:
Given in the question an expression
√(16 a^8 b^-2)
This expression can also be written as
√16 . √a^8 . √b^-2
Now as we know that
√16 = √4² = 4
√a^8 = √(a². a² . a² . a²) = √a².√ a².√ a².√ a² = a . a . a . a = a^4
√b^-2 = √1/b² = √1 ÷ √b² = 1 ÷ b = 1/b
Rearranging them
4 a^4 1/b = 4 a^4/b