One Means of Increasing the Amount of Calories Available for Human

One means of increasing the amount of calories available for human consumption would be to

A) use the world's grain crops to raise more herbivorous livestock.
B) encourage people to simplify their diets by selecting foods from the bottom of the food web.
C) use environmentally safe pesticides to eliminate the insects that compete for our food.
D) prohibit the commercial marketing of secondary and tertiary consumers.