Self-study
After purchasing a pot-bellied pig at the pet store in Springfield, Amy was informed by a Springfield city official that Conclusion she would not be allowed to keep the pig as a pet, since Support city codes classify pigs as livestock, and Support individuals may not keep livestock in Springfield.
Remember the Domain
To understand the argument in the stimulus, it's important to note that the city official's statements are the argument, with Amy's purchase given as context. So, with the context of Amy purchasing a pot-bellied pig in Springfield, the city official concludes that Amy won't be allowed to keep the pig as a pet. In support, the official cites some rules: pigs are classified as livestock, and individuals aren't allowed to keep livestock in Springfield.
We can also represent the argument with a conditional diagram:
Domain: Springfield City
Rule 1: pig → livestock
Rule 2: livestock → /keep as pet
______
Combined Rule: pig → /keep as pet
Objective: Identify a Necessary Assumption
Looking at the argument in diagram form, it seems like it's valid: Amy isn't allowed to keep her pig as a pet. But remember the domain! These are the rules in the city of Springfield. So the author is assuming that Amy plans to keep the pig in Springfield. Sure, Amy bought the pig in Springfield, but we don't know if she's planning to stay there. Maybe she lives in another town, and travelled to buy a pig from this particular pet store. The rule about not keeping livestock only applies in Springfield, so if Amy is planning to keep the pig elsewhere, maybe she will be allowed to keep it as a pet.
We can tell this is a necessary assumption because if we don't assume Amy plans to keep the pig in Springfield, the argument falls apart. Springfield's city rules have no bearing on whether Amy would be allowed to keep the pig as a pet elsewhere. If Amy isn't staying in Springfield, the city official's conclusion loses all its support. The correct answer will state the assumption that Amy is planning to keep the pig in Springfield.
2.
The city official's argument depends ██ ████████ █████ ███ ██ ███ ██████████
a
Amy lives in ████████████
If Amy lives in Springfield, that's reasonably equivalent to the assumption we identified, that Amy is planning to keep her pig in Springfield. And that makes this assumption logically necessary to the argument: if Amy did not live in Springfield, then Springfield's rules against keeping livestock would be irrelevant, and the official's argument would fall apart.
Because we're working with a fairly straightforward conditional argument, the assumption necessary to fill in the gap is also sufficient. All we need to know is that this assumption is necessary; that it happens to be sufficient as well isn't a problem.
b
Pigs are not ██████████ ██ ████ ██ ████████████
The official states that pigs are classified as livestock, so whether or not they're also classified as pets doesn't make a difference. We already know that the rule about not keeping livestock in Springfield is triggered, so the only thing left that's necessary to assume is that Amy is actually staying in Springfield.
c
Any animal not ██████████ ██ █████████ ███ ██ ████ ██ ████████████
We know the pig is livestock, so the rules that apply to non-livestock animals don't make a difference. The conclusion that that Amy won't be allowed to keep her pig doesn't depend on what animals people are allowed to keep. Even if it were forbidden to keep any kind of animal as a pet in Springfield, that wouldn't harm the official's argument.
d
Dogs and cats ███ ███ ██████████ ██ █████████ ██ ████████████
Like (C), this isn't relevant to the official's argument, so isn't necessary to assume. What types of animals people are allowed to keep in Springfield doesn't make a difference to the claim that Amy won't be allowed to keep her pig. Even if dogs and cats were classified as livestock, and thus banned, the argument would still stand.
e
It is legal ███ ███ ██████ ██ ████ ████ ██ ████████████
The purchase of the pig isn't at issue, only whether Amy will now be allowed to keep it. The rules that apply to pet stores aren't relevant to the official's claim about the rules that apply to Amy. If it were illegal to sell pigs, that wouldn't affect the argument.