Which of the following statements about the vertical temperature structure of the Earth atmosphere are correct? 1. In the stratosphere, temperature increases with altitude. 2. In the mesosphere, temperature decreases with altitude. 3. The lowest temperature of the atmosphere is recorded in the upper part of the mesosphere. 4. The tropopause acts approximately as an isothermal zone. Select the correct answer using the code given below.

Introduction / Context:
The atmosphere is divided into several layers based on temperature trends with height: troposphere, stratosphere, mesosphere, and thermosphere. Understanding how temperature changes in each layer is fundamental in climatology and physical geography. This question presents four statements about the temperature structure and asks you to identify which ones are correct. It requires a clear mental picture of the vertical temperature profile of the atmosphere.

Given Data / Assumptions:

• Statement 1: In the stratosphere, temperature increases with altitude.
• Statement 2: In the mesosphere, temperature decreases with altitude.
• Statement 3: The lowest temperature of the atmosphere is recorded in the upper mesosphere.
• Statement 4: Tropopause is approximately an isothermal zone (temperature is nearly constant with height).
• The task is to select the combination of statements that correctly describes real atmospheric behaviour.

Concept / Approach:
In the troposphere, the lowest layer of the atmosphere, temperature generally decreases with altitude at an average environmental lapse rate, because the surface is the main source of heating by absorbing solar energy and re radiating infrared. Near the top of the troposphere lies the tropopause, where temperature becomes nearly constant with height, so it is often described as an isothermal layer or zone. Above the tropopause, in the stratosphere, temperature increases with height because of absorption of ultraviolet radiation by ozone, creating a temperature inversion. Above the stratosphere is the mesosphere, in which temperature again decreases with altitude, reaching very low values at the mesopause, which separates the mesosphere from the thermosphere. The mesopause is typically the coldest region of the atmosphere. Therefore, statements 1, 2, 3, and 4 are all correct.

Step-by-Step Solution:

Verification / Alternative check:
Standard atmospheric science diagrams of temperature versus height show a decrease in temperature through the troposphere, a near constant temperature at the tropopause, an increase through the stratosphere, a decrease again through the mesosphere, and then a rapid increase in the thermosphere. They also label the mesopause as the coldest region of the atmosphere. Climatology textbooks use similar descriptions, emphasising the temperature inversion in the stratosphere and the approximate isothermal character of the tropopause. These sources confirm each of the four statements, supporting the choice of all four as correct.

Why Other Options Are Wrong:

1 and 2 only is wrong because it excludes statements 3 and 4, both of which are correct according to the known vertical temperature profile.

1, 2 and 3 only is incorrect because it omits statement 4, which correctly describes the tropopause as an approximately isothermal zone.

3 and 4 only is wrong because it leaves out statements 1 and 2, which are also correct about the stratosphere and mesosphere.

Common Pitfalls:
Students often remember that temperature decreases with height in the troposphere but may not recall the inversions and changes in higher layers. Some may be unsure about the tropopause being nearly isothermal or may misplace the coldest region. To avoid confusion, it is helpful to memorise the typical temperature pattern: troposphere (decrease), tropopause (almost constant), stratosphere (increase), mesosphere (decrease, with coldest temperatures at the mesopause). With this pattern in mind, it becomes clear that all four statements in the question are correct.

Final Answer:
Therefore, the correct choice is that all four statements 1, 2, 3 and 4 are correct, corresponding to option D.