Why is anaerobic respiration considered less efficient than aerobic respiration?

a
More oxygen is required for anaerobic respiration than for aerobic respiration.
b
More ATP molecules are gained in aerobic respiration than in anaerobic respiration.
c
Less lactic acid is formed during anaerobic respiration than during aerobic respiration.
d
Less energy is required during anaerobic respiration than aerobic respiration.

b

More ATP molecules are gained in aerobic respiration than in anaerobic respiration.