3) Suppose a consumer can purchase only two goods, beef and chicken. If the price of beef falls (with all other variables held constant), and the consumption of chicken increases, we can conclude that the increased consumption of chicken is due to A) neither the income effect nor the substitution effect. B) the income effect only. C) both the income effect and the substitution effect. D) a change in the consumer's preference toward chicken. E) the substitution effect only