The sun is millions of kilometers away. how can heat from the sun get there?

Solar radiation is light energy from the Sun. So you've got the Sun. Millions of kilometers away from the Earth it sits there with all sorts of nuclear reactions going on. It's constantly giving off a huge amount of energy and radiation.

it's d. aerobic]

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.