Which statement about the cosmic microwave background is not true?

It is thought to be radiation that began its journey to our telescopes when the universe was about $380,000$ years old.

With the exception of very small variations, it appears essentially the same in all directions in which we look into space.

It is the result of a mixture of radiation from many independent sources, such as stars and galaxies.

Its spectrum has the shape of an essentially perfect thermal radiation spectrum.