John applies a small amount of liquid between his dog's shoulder blades each month. The liquid
helps prevent insects from bothering his dog. Lately, the liquid does not keep fleas off his dog
What is the likely cause of this change?
A. The fleas that survived exposure to the liquid once have produced offspring that are resistant to
the liquid.
B. The weather conditions have changed. There are more fleas living in John's yard.
C. The liquid has changed the dog's fur over time. Now the liquid is absorbed into the fur rather
than staying on the skin.
D. John gives his dog a bath after applying the liquid and the liquid is not able to work correctly.