18: D, homologous
20: B, DNA
I can’t see 17 or 19!
Answer:
I think it is white and is looks like powder and is has a strong smell.
Explanation:
If I'm right please give brainliest. sorry if wrong.
C. The nervous system sends signals to make muscles move.
Radioactive decay occurs when an atom has either to many or to few neutrons and becomes unstable and start to emit radio active radioactive radiation and the atom start to decompose.
At the end two things can happen either the atom will transform in a new element with a lower atomic # and atomic mass # or the remaining neutron will transform into an electron and be on its own way
