Question

### Origin of Earth's Water

Three scientists discuss the primary origin of Earth's oceans:

*Scientist 1*
Earth's water was primarily delivered by carbonaceous chondrite meteorites during the late accretion phase, after the planet's core had fully formed. The primary evidence for this is the deuterium-to-hydrogen ($D/H$) ratio of Earth's ocean water, which closely matches that of carbonaceous chondrites. In contrast, most comets have a $D/H$ ratio that is nearly twice as high as that of Earth's oceans, making them an unlikely source.

*Scientist 2*
Earth's water originated from the adsorption of solar nebula gas onto silicate dust grains during the planet's initial accretion. As Earth grew, this water was trapped in the mantle and later released to the surface through volcanic outgassing. The matching $D/H$ ratio of chondrites is a coincidence; deep-mantle rocks show a much lower $D/H$ ratio, indicating a primordial nebular origin.

*Scientist 3*
Comets from the outer solar system were the primary source of Earth's water. During the late heavy bombardment period, intense cometary impacts delivered volatile-rich ice. While early measurements showed high $D/H$ ratios for comets, recent data from Jupiter-family comets show $D/H$ ratios identical to Earth's oceans. Since comets are composed almost entirely of ice, they are a far more efficient delivery mechanism than rocky chondrites.

Based on the viewpoints of Scientists 1, 2, and 3, match each point of disagreement to the description of the scientists who hold conflicting views on that topic.