In a positive phototropic response of a coleoptile, the region of greatest curvature is brought about by the

• A.movement of auxins away from the region of curvature
• B.even distribution of auxins in all parts of the coleoptile
• C.inhibition of growth by auxins in the region f smaller curvature
• D.concentration of auxins in the region of curvature
• E.absence of auxins in the coleoptile