Answer:
Fourth option
Explanation:
The discriminant of a quadratic in the form of

is

Here , b is -6, a is 1, and c is 9
So we get

So the discriminant is 0.
Since we have a discriminant of 0, this means our x intercept lie at the vertex thus we only have 1 real solution.
If we had a positive discriminant, that means we have two x intercepts(two rational roots)
Why? Because in the quadratic formula, notice that plus minus symbol. It means we have two possible x intercepts.
If we had a negative discriminant, we will have 2 imaginary roots
Why? Because not only we have a plus or minus symbol, you will learn that the square root of a negative number is an imaginary, complex number.
So the answer is D.