Which of the Following Accurately Describes 18O/16O Ratios of the World's

Which of the following accurately describes 18O/16O ratios of the world's 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 evapouration to be effective and both isotopes remain in the ocean.