Which of the Following Accurately Describes ¹⁸O/¹⁶O Ratios of the Worlds

Which of the following accurately describes ¹⁸O/¹⁶O ratios of the worlds oceans?

A) Because ¹⁸O evaporates more readily than ¹⁶O, the oceans have a higher relative abundance of ¹⁶O during warm periods and a more balanced ratio when there is less evaporation.
B) The higher the ratio of oceanic ¹⁸O/¹⁶O, the warmer the temperatures because the ¹⁶O will have been mostly evaporated from ocean waters.
C) During periods of colder temperature ¹⁶O is locked up in snow and ice and the oceans have a higher preponderance of ¹⁸O; during warmer periods the isotope ratio is lower.
D) The ¹⁸O/¹⁶O ratio is low during colder temperatures because temperatures are too low for evaporation to be effective and both isotopes remain in the ocean.