There must be some other explanation for why it takes less time to care for 8 pets than it takes to care for 5 pets. So we turn to our second hypothesis. Maybe kids with more pets had pets that took less time to care for.

This hypothesis also has two parts:

Part 1: Some animals take less time to care for than others. 
Part 2: Kids with more pets are more likely to own these "low-maintenance" animals.

If both parts are true, then the evidence supports this hypothesis.

Let's see . . .