Which of the following statements is/are true? 1. The angle of the axis in relation to the plane in which the earth revolves around the sun is not constant. 2. The amount of energy given off by the sun changes with the transparency of the atmosphere. Select the correct answer using the code given below.

Statement 1 is true because Earth's axial tilt, or obliquity, is not constant. It varies between approximately 22.1° and 24.5° over a 41,000-year cycle known as a Milankovitch cycle [1]. Currently, the tilt is about 23.4° and is slowly decreasing. Statement 2 is false because the amount of energy given off by the sun (solar irradiance) is an intrinsic property of the sun's activity, such as sunspot cycles, and is measured as the solar constant at the top of the atmosphere. While the transparency of the atmosphere (affected by clouds, dust, and aerosols) significantly influences the amount of insolation that reaches the Earth's surface, it does not change the amount of energy actually 'given off' by the sun itself [2]. Therefore, only the first statement regarding the variation of the axial tilt is correct.

Sources

1. [1] https://www.sciencedirect.com/topics/earth-and-planetary-sciences/milankovitch-cycle
2. [2] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > Variability of Insolation at the Surface of the Earth > p. 67