Country A and country B initially have the same per capita income. Suppose that A sustains an annual growth rate of 3.5 percent, while the annual growth rate of country B is 1.75 percent. The "rule of 70" indicates that after forty years, the per capita income of country A will be approximately _________ that of country B.A) one-half
B) 70 percent greater than
C) twice
D) four times