Your answer to this question is definitely C!
The coordinates of C are (3, 2)
The coordinates of D are (4, 1)
Most textbooks interpret standard form of a quadratic function to be as follows:
f(x) =

In the function f(x) =

, notice we do not have a value for "c". Just place a "0" in for the c and you have standard form.
the criteria for standard form:
1. All like terms are combined
2. Degree must drop from left to right
3. The leading coefficient cannot be equal to zero.
I think the answer would be 1.8