The dissolved materials in seawater are thought to originate from chemical weathering of rocks on the continents and also from
a) benthonic.
b) plankton.
c) out-gassing of elements from earth's interior.

Option (C)

Explanation:

The out-gassing is usually defined as the process by which gases such as carbon dioxide, water vapor, sulfur dioxide, and nitrogen are released during the release of pressure from the earth's molten rocks. This process takes place due to the increase in temperature. These gases are responsible for the formation of the atmosphere over millions of years.

Thus, the dissolved materials that are found in the seawater are mainly originated from the out-gassing of elements from the interior of the earth and also from the chemical weathering of rocks on the continents.

Thus, the correct answer is option (C).