How would you explain the presence of bacterial growth in the control FTM tube? What would be the effect of using FTM tubes with broad pink zone?

Twenty fruit flies are placed in each of four glass tubes. The tubes are sealed. Tubes I and II are partially covered with black paper; Tubes III and IV are not covered. The tubes are placed as shown. Then they are exposed to blue light for five minutes. The number of flies in the uncovered part of each tube is shown in the drawing.

These data show that these flies respond to (respond means move to or away from):

Twenty fruit flies are placed in each of four glass tubes. The tubes are sealed. Tubes I and II are partially covered with black paper; Tubes III and IV are not covered. The tubes are placed as shown. Then they are exposed to blue light for five minutes. The number of flies in the uncovered part of each tube is shown in the drawing.

These data show that these flies respond to (respond means move to or away from):

Explanation:

a sperm cell fertilizes an egg cell.