Hello,
I got this question correct and can see how B must be true, but I was also tempted by E because of the idea of staying fit, which is mentioned only once in the first sentence and then not mentioned again. I am wondering if the second sentence implies that if a dog does not meet intensely exercise as much as it needs (in order to stay fit, as opposed to, for example, the purpose of staying alive) then it is more troublesome? I guess I am wondering whether there are any assumptions surrounding the idea of staying fit. For me, I thought it might be the case that the argument is assuming that if dogs are not exercised to the level of intensity
that they need in order to stay fit, then they become more troublesome. However, I am not sure if this is already implied by the second sentence. Thanks so much for your help!