How does the graph of a parabola change when you change the value of k? a. it shifts vertically c. it shifts horizontally b. no change d. both a and c

The correct option  is IT SHIFTS VERTICALLY.
In parabola graphs, the vertical shift refers to the amount that the graph shift vertically and this is determined by the K value in the vertex form of a quadratic equation. The effect of K is that it shifts the parabola graph up and down. The amount of the K coefficient is the vertical shift of the parabola.