WILL GIVE A BRAINLIEST!!!

In a quadratic function of the form ax^2+bx+c, which of the following is not true?
A.
The y-intercept is c.
B.
If a is positive, the parabola opens up.
C.
The vertex has an x-coordinate of -b/2a.
D.
The axis of symmetry is the line y=-b/2a.