The primary purpose of the passage is to
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[[snippet]]The first paragraph describes the hormone oxytocin, the second describes one of its functions and the third describes its evolutionary history.
Incorrect.
[[snippet]]Neuroendocrine cells are only discussed in the first paragraph and even there the function of neuroendocrine cells in the body is not explained (only that they create oxytocin).
Incorrect.
[[snippet]]This answer choice is too broad. The passage investigates only one hormone produced in the hypothalamus: oxytocin.
Incorrect.
[[snippet]]This answer choice is too narrow. Vassopressin's similarity to oxytocin is the topic of the third paragraph only.
Incorrect.
[[snippet]]This answer choice is too narrow. One function of oxytocin in mammalian females is the topic of the second paragraph.