Why is the comsic background radiation so weak today?

Question

a
The Big Bang wasn't as powerful as originally suspected
b
The energy from cosmic background radiation is absorbed by galaxies
c
Cosmic background radiation cannot be measured by current science equipment
d
It started as a fixed amount that has been spread out wide across the entirety of the Universe

Answer 1

d) It started as a fixed amount that has been spread out wide across the entirety of the Universe