What are the main vertical layers of Earth's atmosphere and their approximate altitude ranges?

• A. Troposphere (surface to ~8–15 km), Stratosphere (~15–50 km), Mesosphere (~50–85 km), Thermosphere (~85–600+ km), Exosphere (beyond ~600 km)
• B. Troposphere (surface to ~100 km), Stratosphere (~100–200 km), Mesosphere (~200–400 km), Thermosphere (~400–1000 km), Exosphere (beyond ~1000 km)
• C. Troposphere (surface to ~0–12 km), Stratosphere (~12–50 km), Mesosphere (~50–80 km), Thermosphere (~80–700 km), Exosphere (beyond ~700 km)
• D. Troposphere (surface to ~20–25 km), Stratosphere (~25–45 km), Mesosphere (~45–70 km), Thermosphere (~70–120 km), Exosphere (beyond ~120 km)

Answer: (A)

The main idea is that Earth’s atmosphere is organized into distinct vertical layers, each with its own typical altitude range and behavior: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. Starting from the surface, the troposphere is where weather happens and it extends roughly to about 8–15 km. Above it, the stratosphere contains the ozone layer and its temperature tends to rise with height, roughly from 15 to 50 km. The mesosphere sits above that, with temperatures generally cooling as you go up to about 50–85 km. Above the mesosphere is the thermosphere, where the air is extremely thin and temperatures can rise with altitude, spanning roughly 85 to 600+ km. Finally, the exosphere lies beyond, gradually fading into space, starting around 600 km and continuing outward.

These ranges are approximate and can vary with latitude and solar activity, but they match the standard teaching of the five-layer structure and the usual boundary markers (tropopause near the top of the troposphere, stratopause around the top of the stratosphere, mesopause near the top of the mesosphere, and thermopause serving as the outer boundary of the thermosphere). The other options mix the boundary heights in ways that don’t align with how the layers are commonly defined, so they’re less accurate representations of the typical altitude ranges.