In the past, infants who were not breast-fed were fed cow's milk. ████ ███████ █████ ████████ ████ █████ ████ ███ ██ ███████ ██████ ██ ███████ ██ ███ ███████ █████ █████████ ███ ████ ███ ███████ ████████████████ ██████████ ███████████ █████ ██ ████████ ████ ████ ██████ ███ ██████ ████████████ █████ ███ ██ ████████ ████████ █████ ███████ ██ ███ █████████ ██ ███████ ██████ ██ ███████ █ ███████████ ██████████ ████████ ████████ ███ ███ ████████ ███████
This stimulus presents a clean fact pattern from which we can reasonably (though not validly – never validly) infer causality. Think of the cow milk kids and the breast milk kids as experimental and control groups, respectively. They both started off without scurvy. Then we started boiling the cow milk and those kids got scurvy. The reasonable conclusion? Something about boiling the cow's milk makes it scurvylicious.
Which one of the following ██ ████ ████████ █████████ ██ ███ ███████████ ██████
Boiled cow's milk █████ ████ ███████ █ █████████ ██ ███████ ████ ████ ███ ████ ██████ ██ ████████ █████
(A) matches the causal inference you should aspire to anticipate after reading the stimulus. Scurvy is caused by a vitamin C deficiency, and (A) provides a mechanism by which drinking boiled cow's milk would result in that deficiency.
For people caught up on "the same amount" – (A) does indeed require the very reasonable assumption that babies drink similar-ish amounts of boiled cow's milk as they would breast milk. This is an MSS question – reasonable assumptions informed by how the real world works are allowed.
Infants who consume █████ ████ ████ ███ ███ ████ ██████ ██████████ ████████ ███████████ █████ ████████████████ ███████████
"Frequently" is the unsupported term here. The stimulus tells us these GI infections exist, but doesn't tell us how frequent they are.
It's interesting to note here that while we'd usually consider the word "frequently" quite weak (it's not as strong as "usually", for example), it's acting like a somewhat strong word here. (B)'s wrongness lies in the difference between the stimulus' "GI infections happen sometimes" and the answer choice's "GI infections happen a lot."
Mother's milk can █████ ████████████████ ██████████ ██ ████████
While this is possible, the only milk associated with GI infections in the stimulus is unboiled cow's milk.
When doctors advised ████ █████ ████ ███ ██ ███████ ██████ ██ ███████ ████ ███ ███ ████ ████ ██████ ███ ██████ ██ ███████ █ ███████████
This is possible, but it's equally likely (or really, much more likely) that the doctors didn't realize boiling the milk would reduce its available vitamin C.
When doctors advised ████ █████ ████ ███ ██ ███████ ██████ ██ ███████ ████ ███████ ███ ███ ███████████ █████ ████████
The stimulus does distinguish between two groups of mothers (breast-fed and non-breast-fed), but we're given no information comparing the size of those two groups.
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