Answer
b
Explanation
The opposite or reverse of square root is squared. When you take a number and the square it, to get the number back you just find its square root.
For example,
2 × 2 = 4
√4 = 2
∴ so we can use this concept to solve, √b×√b as follows:
√b × √b = √(b×b)
= √b²
= b