Three colonies of insects were each treated with a different pesticide over an 8-week period to test the effectiveness of the three pesticides. Colonies A, B, and C were treated with Pesticides A, B, and C, respectively. Each pesticide was applied every 2 weeks to one of the three colonies over the 8-week period. The bar graph above shows the insect counts for each of the three colonies 0, 2, 4, 6, and 8 weeks after the initial treatment.
Which of the following colonies showed a decrease in size every two weeks after the initial treatment with pesticide?
I.Colony A
II.Colony B
III. Colony C

Options

A. I only
B. III only
C. I and II only
D. I, II, and III

Answer

C

Explanation

According to the bar graph, the number of insects in colony A at week 0 was approximately 80, and this number decreased over each respective two-week period to approximately 50, 32, 25, and 18. Similarly, the graph shows that the number of insects in colony B at week 0 was approximately 64, and this number also decreased over each respective two-week period to approximately 60, 40, 38, and 10. Finally, the graph shows that the number of insects in colony C at week 0 was approximately 58, however, the number of insects increased in week 2, to approximately 140. Therefore, only colony A and colony B showed a decrease in size every two weeks after the initial treatment.
Choice A is incorrect. Colony B also showed a decrease in size every two weeks. Choices B and D are incorrect. Colony C showed an increase in size between weeks 0 and 2.