Question

how do humans cycle carbon from the biosphere to the atmosphere? (1 point)
by driving cars that use gasoline for fuel
by eating plants
by respiration
by planting vegetable crops

Explanation:

• Option "by driving cars that use gasoline for fuel": Burning gasoline (a fossil fuel) releases carbon dioxide from the geosphere (fossil fuels) to the atmosphere, not directly from the biosphere.
• Option "by eating plants": Eating plants transfers carbon within the biosphere (from plants to humans) and doesn't release it to the atmosphere.
• Option "by respiration": Humans (part of the biosphere) perform cellular respiration, which breaks down organic matter (containing carbon) and releases carbon dioxide ($\ce{CO_2}$) into the atmosphere. This is a direct transfer of carbon from the biosphere (human bodies, which are part of the biosphere) to the atmosphere.
• Option "by planting vegetable crops": Planting crops takes carbon from the atmosphere (via photosynthesis) and stores it in the biosphere (plants), moving carbon into the biosphere, not out to the atmosphere.

Answer:

C. by respiration