Number of cases has reduced in the town
Option A is incorrect
Explanation: Say previously the number of dog owners were 100 and of them 50 used to feed choco to their dogs.
Scenario 1: Number of dog owners has been constant for last 3 years ==> still 50 of them feed choco to their dogs.
Scenario 2: Number of dog owners has reduced in the last 3 years to 70 ==> still 50 of them feed choco to their dogs and few of them don't take their dogs to the vet. So, the number of people feeding choco to their dogs has not reduced.
Scenario 3: Number of dog owners has increased in the last 3 years to 120 ==> still 50 of them feed choco to their dogs and few of them don't take their dogs to the vet. So, the number of people feeding choco to their dogs has not reduced.
So, negation of the assumption doesn't break the conclusion.
Option C is correct
Whether with an increased availability of dog-safety kits, more and more pet owners have opted to treat their pets at home to reduce wastage of time transporting the pet to a veterinary clinic.
Scenario 1: availability of dog-safety kits has increased, so fewer people are taking their dogs to the vets and rest are treating them at home, so the number of people feeding choco to their dogs hasn't reduced.
Scenario 2: dog-safety kits are not easily available and fewer people are taking their dogs to the vets, treatment at home is low, thus the number of people feeding choco to their dogs has reduced.
Negating option C gives different answers
Hence, option C is correct