Dr. F. Went noted that if coleoptile tips were removed and placed on agar for one hour, the agar would produce a bending when placed on one side of freshly-cut coleoptile stumps. Of what significance is this experiment?

• A

  It made possible the  isolation and exact identification of auxin

• B

  It is the basis for quantitative determination of small amounts of growth-promoting substances

• C

  It supports the hypothesis that IAA is auxin

• D

  It demonstrated polar movement of auxins