Megan experimented with growing mold. she took 3 pieces of bread from the same loaf and placed each into a plastic sandwich bag. before sealing the bag, she added 5 drops of water to each slice. next, she placed one bag on her window sill, one in a dark cabinet, and one in a room away from sunlight. megan concluded that the different amount of mold that grew on each slice was due to the amount of light it received. is this a valid conclusion?

a) yes, because the light was the manipulated variable.

b) yes, because the light was the controlled variable.

c) no, because the light could not have affected the growth.

d) no, because the light should have been the same for each bread slice.