In a photo-tropic experiment, young seedlings in a box were subjected to light from one direction. The seedling continue to grow erect. Which of the following statement is correct

A. Only the tip of the seedling received the light
B. The light was not strong enough
C. The seedlings were rather too young
D. The tip of the seedling may have been covered
E. The box containing the seedling should have been placed on a laboratory bench