Which of the following is/are cited by the scientists as evidence/evidences for the continued expansion of universe? 1) Detection of microwaves in space 2) Observation of redshift phenomenon in space 3) Movement of asteroids in space 4) Occurrence of supernova explosions in space Select the correct answer using the codes given below:

The correct answer is A (1 and 2). Two observations are the classic evidence for an expanding universe. The first is redshift (statement 2). Edwin Hubble's work in the 1920s showed that distant galaxies' light is shifted to longer wavelengths, and the shift grows with distance. That is the direct signature of space stretching, and it is the basis of Hubble's law. The second is the detection of cosmic microwave background radiation (statement 1), discovered in 1965. It is the cooled afterglow of a hot, dense early universe, and its existence fits an expanding, cooling universe.

• Statement 3 (asteroids) is wrong. Asteroid motion is governed by gravity within the solar system and says nothing about cosmic expansion.
• Statement 4 (supernovae) is not cited in this context. Type Ia supernovae gave evidence of accelerating expansion only in 1998, a conclusion that was not part of the standard evidence set in 2012 and is not the basis of this option set.

Core concept: the Big Bang model and Hubble's law. This links to Geography and Science and Technology, and to Mains questions on how observational evidence supports scientific theories.

Trap: candidates pick option C because supernovae feel like a cosmology topic. Statement 3 is the clear misfit, so C fails.