Evidence that the cosmic background radiation really is the remnant of a big bang comes from predicting characteristics of remnant radiation from the big bang and comparing these predictions with observations. four of the five statements below are real. which one is fictitious?
the cosmic background radiation is expected to have a temperature just a few degrees above absolute zero, and its actual temperature turns out to be about 3 k (actually 2.7 k)

a. the cosmic background radiation is expected to have a perfect thermal spectrum, and observations from the cobe spacecraft verify this prediction.
b. the cosmic background radiation is expected to contain spectral lines of hydrogen and helium, and it does
c. the cosmic background radiation is expected to look essentially the same in all directions, and it does.
d. the cosmic background radiation is expected to have tiny temperature fluctuations at the level of about 1 part in 100,000. such fluctuations were found in the cobe data.