Correct Option: D

The troposphere is the lowest portion of Earth's atmosphere. The average depth of the troposphere is approximately 17 km (11 mi) in the middle latitudes. It is deeper in the tropics, up to 20 km and shallower near the Polar Regions, at 7 km in summer, and indistinct in winter. It contains approximately 80% of the atmosphere's mass and 99% of its water vapor and aerosols.