Suppose f(x) = x2 and g(x) = 7x2. which statement best compares the graph of g(x) with the graph of f(x)?

a. the graph of g(x) is the graph of f(x) vertically stretched by a factor of 7.
b. the graph of g(x) is the graph of f(x) shifted 7 units up.
c. the graph of g(x) is the graph of f(x) horizontally stretched by a factor of 7.
d. the graph of g(x) is the graph of f(x) vertically compressed by a factor of 7.