Question

what was discovered in 1965 and is believed to be leftover thermal energy from the big bang?
red shift
the eagle nebula
the doppler effect
background radiation

Explanation:

In 1965, Arno Penzias and Robert Wilson discovered cosmic microwave background radiation, thought to be leftover thermal energy from the Big - Bang. Red shift and the Doppler effect are related to motion and light wavelength changes, and the Eagle Nebula is a star - forming region, not related to Big - Bang leftover energy.

Answer:

D. background radiation