What is a quasar? 1.A star that emits intense radio and light energy.
2.A system of stars held together by gravity.
3.Two stars moving around each other.
4.A collapsed star emitting no light.
5.A star that emits a repeated radio signal.

i think 2 sorry if i am wrong

Explanation:

A quasar (/ˈkweɪzɑːr/; also known as a quasi-stellar object, abbreviated QSO) is an extremely luminous active galactic nucleus (AGN), in which a supermassive black hole with mass ranging from millions to billions of times the mass of the Sun is surrounded by a gaseous accretion disk. As gas in the disk falls towards the black hole, energy is released in the form of electromagnetic radiation, which can be observed across the electromagnetic spectrum. The power radiated by quasars is enormous; the most powerful quasars have luminosities thousands of times greater than a galaxy such as the Milky Way. Usually, quasars are categorized as a subclass of the more general category of AGN. The redshifts of quasars are of cosmological origin.

a massive and extremely remote celestial object, emitting exceptionally large amounts of energy and typically having a starlike image in a telescope. It has been suggested that quasars contain massive black holes and may represent a stage in the evolution of some galaxies.

1.solid

2.carbon dioxide

3.helium