According to the passage, scientists have concluded which of the following from the discovery of the large amount of deuterium found in comets

A． Comets do not contain enough deuterium to have solely created the Earth's oceans.
B． Given the ratio of deuterium to ordinary hydrogen in seawater, comets cannot have contributed to the Earth's oceans.
C． It is likely that comets contain less Xenon than meteorites do.
D． Given the low level of deuterium in the waters of Earth's oceans, comets cannot be its sole source.
E． Comets now play a greater role in the creation of the Earth's oceans than was previously thought.