What causes a green plant exposed to the light, on only one side, to bend towards the source of light as it grows?

• A

  Light stimulates plant cells on the lighted side to grow faster.

• B

  Auxin accumulates on the shaded side, stimulating greater cell elongation there.

• C

  Green plants need light to perform photosynthesis.

• D

  Green plants seek light because they are phototropic.