Help pls Suppose f(x)=x^2 and k(x)=7x^2 which statement best compares the graph of k(x) with the graph of f(x)

A. The graph of k(x) is the graph of f(x) shifted 7 units right

B. The graph of k(x) is the graph of f(x) horizontally stretched by a factor of 7

c. The graph of k(x) is the graph of f(x) vertically stretched by a factor of 7

d. The graph of k(x) is the graph of f(x) vertically compressed by a factor of 7