The correct answer is 1 and 2. Key Points Big Bang Theory: ​The Big Bang Theory is the prevailing cosmological model for the birth of the universe. It states that at some moment all of space was contained in a single point of very high-density and high-temperature state from which the universe has been expanding in all directions ever since. According to this theory, the universe, ever since its birth, is expanding in all directions. In 1964, the cosmic microwave background radiation was discovered, which was crucial evidence in favour of the Big Bang model. Other evidence such as cosmological redshift, gravitational waves, etc. has added weight to the big bang theory. ​Evidence for the continued expansion of the universe: ​​Cosmic microwave background (CMD): ​​​A sensitive radio telescope shows a faint background glow. This glow is strongest in the microwave region of the radio spectrum, and hence it is called a cosmic microwave background. As CMB is the radiation left over from an early stage in the development of the Universe, its discovery is considered a landmark test for the Big Bang model of the Universe. Hence, statement 1 is correct.​​ ​Doppler-shift or Redshift and Blueshift: ​Redshift and Blueshift describe how light changes as objects in space (such as stars or galaxies) move closer or farther away from us. The concept is key to charting the universe’s expansion. When an object moves away from us (Doppler-shifted to lower frequencies), the light is shifted to the red end of the spectrum, as its wavelengths get longer. If an object moves closer (Doppler-shifted to higher frequencies), the light moves to the blue end of the spectrum, as its wavelength gets shorter. American astronomer Edwin Hubble was the first to describe the redshift phenomenon (galactic redshift) and tie it to an expanding universe (galaxies are drifting apart). Hence, statement 2 is correct.