.In a study of energy flow, the following data were collected:

Each human requires 55 grams of protein per day. An acre of soybeans produces 200,000 grams of protein per year. A cow grazing on one acre of land produces 19,000 grams of protein per year.

Based on these data, an acre of land would support:

10 humans per year on a diet of soy, or 0.9 human per year on a diet of beef.

Which of the following statements best explains these relationships in terms of energy transfer?

A) Humans are better adapted to make efficient use of soy protein than beef protein, so they can extract more energy from a gram of soy protein than from a gram of beef protein

B) A cow can harvest energy only at a certain rate, so adding another cow to the acre of land would double the number of humans supported by the acre.

C) Preparing meat for human consumption takes more energy per gram of protein than preparing soy for consumption.

D) Only 10% of the energy on each level of the trophic pyramid is available for use by the next level. The rest is lost as heat or used for growth and repair.