Atmospheric layers and temperature profile: identify the wrong statement regarding the mass distribution, temperature trend, and position of the troposphere and stratosphere within the earth system up to roughly 200 km.

Introduction / Context:
Environmental engineering frequently draws on basic meteorology to understand pollutant dispersion, stability, and ozone shielding. This question checks conceptual understanding of where air mass is concentrated and how temperature changes with height in the lowest two layers: the troposphere and the stratosphere.

Given Data / Assumptions:

• Focus on troposphere vs stratosphere only.
• Qualitative temperature trends with altitude are sufficient.
• Heights are approximate; the atmosphere extends well beyond 200 km, but 200 km is a commonly cited round figure in simple descriptions.

Concept / Approach:
The troposphere contains the majority of atmospheric mass (on the order of 75–80%) and exhibits a temperature decrease with altitude on average (the environmental lapse rate). The stratosphere sits above the troposphere and displays increasing temperature with height due to ozone absorption of ultraviolet radiation. Therefore, any statement that assigns most mass to the stratosphere or says that stratospheric temperature steadily decreases is incorrect.

Step-by-Step Solution:

Verification / Alternative check:
Standard-atmosphere profiles show a 6.5 C per km average tropospheric decrease and a positive gradient in the stratosphere.

Why Other Options Are Wrong:
Option (b): Ozone concentration peaks in the stratosphere above the tropopause; correct.
Option (c): The troposphere hosts weather, clouds, and most water vapor; correct.
Option (d): 200 km is a rounded descriptive figure; while simplification, it is acceptable in many primers.

Common Pitfalls:
Mixing up the sign of the temperature gradient; assuming equal mass per layer by thickness rather than by compression effects.

Final Answer:
Statement (a) is wrong.