Reading Comprehension (RC) | Re: Milankovitch proposed in the early twentieth century that

bpdulog There's no indication that the 18-enriched water turns to ice. It's in the ocean, and the passage doesn't say that the ocean freezes.

However, that doesn't matter anyway. The question is asking us to compare rain from evaporated ocean water with continental ice sheets. That rain is exactly what forms the ice sheets, so they should have roughly the same concentration of oxygen 18 (a very low one, if any at all!).
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