Piper’s cat had fleas and she called the vet to see what she needed to do. She was given a topical treatment to put on her cat. Piper watched as the disgusting fleas began to drop off her cat as they died. Satisfied, she gave it no further thought until a few weeks later, when she saw her cat scratching again. Separating the fur of the fluffy cat, Piper could see more flea dirt! How did the fleas end up back on her cat again?

a. Piper’s cat must have licked off the topical flea treatment.
b. The fleas on Piper’s cat must have become immune to the treatment.
c. Piper’s cat must have been exposed to another animal after the first treatment.
d. Piper did not treat the bedding or carpet where flea eggs must have been hiding.