Question ID:PT1 S3 Q11 Passage:Water vapor evaporated from the ocean contains a greater proportion of oxygen-16 and a smaller proportion of the heavier oxygen-18 than does seawater. Normally, this phenomenon has no effect on the overall composition of the ocean, because evaporated seawater returns to the ocean through precipitation. During an ice age, however, a large amount of precipitation falls on ice caps, where it is trapped as ice. Stem:Which one of the following conclusions about a typical ice age is most strongly supported by the statements above? Correct Answer Choice:BChoice A:The proportions of oxygen-16 and oxygen-18 are the same in vapor from seawater as in the seawater itself. Choice B:The concentration of oxygen-18 in seawater is increased. Choice C:Rain and snow contain relatively more oxygen16 than they do in interglacial periods. Choice D:During the ice age, more of the Earth’s precipitation falls over land than falls over the ocean. Choice E:The composition of seawater changes more slowly than it does in interglacial periods.