Complete these sentences about the formation of a star.

(i) Stars are formed from giant interstellar clouds of gas and ____________________.

(ii) These clouds collapse inwards due to the attractive force of ____________________.

(iii) Before nuclear fusion begins, the hot, dense core formed by this collapse is called a ____________________.

The Big Bang Theory is the primary scientific model describing the origin of the Universe.

State one piece of observational evidence that supports the Big Bang Theory, and explain how this evidence supports the theory.