How does the graph of the parabola change when you change the value of h? a. it shifts to the left c. it shifts to the right b. it shifts vertically d. both a and c

Based on the question, it seems safe to assume that we're talking about a parabola in vertex form: 
y = a(x-h)² + k, where the vertex is located at point (h, k), and the a value determines the direction (positive or negative) and steepness (absolute value of a) of the parabola. 

h is the x value of the vertex. When we change the x value, it will move left or right. I'm not sure why the orders are different (the options go from a to c to b), but the correct is:

It shifts to the left or the right.