Question

1. the coldest layer of the atmosphere. troposphere stratosphere thermosphere mesosphere

Explanation:

To determine the coldest layer of the atmosphere, we analyze each option:

• Troposphere: Temperature decreases with altitude but isn't the coldest overall.
• Stratosphere: Temperature increases with altitude (due to ozone absorption of UV), so it's warmer than the mesosphere.
• Thermosphere: Temperature is very high (though particles are sparse, so "heat" perception is different), but it's not the coldest.
• Mesosphere: As altitude increases in the mesosphere, temperature drops significantly, and it is the coldest layer of the atmosphere, with temperatures reaching as low as -90°C or lower.

Answer:

D. mesosphere