Refer to the figure.
These results indicate that

A) chicks with colored gapes received more food than those with an unaltered gape.
B) chicks with gapes colored red received more food than those with a yellow or unaltered gape.
C) experimentally altering chicks' gapes reduced the amount of food that they received.
D) experimentally altering chicks' gapes did not impact the amount of food they received.