Consider the following pairs : Objects in space : Description 1. Cepheids : Giant clouds of dust and gas in space 2. Nebulae : Stars which brighten and dim periodically 3. Pulsars : Neutron stars that are formed when massive stars run out of fuel and collapse How many of the above pairs are correctly matched?

Only pair 3 is correctly matched because Pulsars are highly magnetized, rotating neutron stars formed from the gravitational collapse of massive stars. Option (b) is the most tempting wrong choice because pairs 1 and 2 are swapped: Cepheids are actually the stars that brighten and dim periodically, while Nebulae are the giant clouds of dust and gas in space. The core concept being tested is the fundamental classification and physical characteristics of different celestial bodies.