Final answer:
Carbon dioxide can be introduced into the hydrosphere through weathering and combustion. These processes are part of the carbon cycle, affecting the balance of carbon in various earth systems.
Step-by-step explanation:
The two activities that can introduce carbon dioxide into the hydrosphere are weathering and combustion. Weathering is a process by which rocks and minerals break down, releasing carbon dioxide into soil and water systems. Combustion, on the other hand, involves the burning of organic material, such as fossil fuels, which releases carbon dioxide into the atmosphere; some of this carbon dioxide then dissolves in bodies of water. These processes are significant in the carbon cycle where carbon dioxide is cycled through different Earth systems, including the hydrosphere.