Answer:
The correct option is C.
Explanation:
If a function f(x) is completely divisible by (x-a), it means (x-a) is a factor of f(x) and x=a is a root of that polynomial.
The given polynomial is

It is given that when David divide the above polynomial by (2x-1), then he get


Since the remainder is zero it means P(x) is completely divisible by (2x-1) or (2x-1) is a factor of P(x).

Add 1 on both the sides.

Divide both sides by 2.

It means
must be a root of the polynomial
.
Therefore, the correct option is C.