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.