Question

### The Origin of Earth's Water

Two scientists discuss the primary source of Earth's water.

Scientist 1
Earth’s water was delivered early in the planet's history by rocky asteroids from the inner solar system, specifically carbonaceous chondrites. These asteroids contain water locked inside their mineral structures. Measurements show that the deuterium-to-hydrogen ($D/H$) ratio of Earth's water matches the $D/H$ ratio found in carbonaceous chondrites, indicating a common origin. Because comets have much higher $D/H$ ratios, they could not have been the main source of Earth's water.

Scientist 2
Earth formed in a region of the solar nebula that was too hot for water to condense, meaning the early Earth was completely dry. Earth's water was delivered much later by icy comets from the cold outer solar system during a period of heavy bombardment. Comets are composed primarily of water ice, making them highly efficient delivery vehicles. While some comets have high $D/H$ ratios, others from the Oort cloud have $D/H$ ratios identical to Earth's ocean water, confirming they were the primary source.

Based on the passage, Scientist 1 claims that Earth's water originated from which of the following sources?