<u>Answer:</u>
Option (3)
The arms mostly contains old blue and blue-white stars
<u>Explanation:</u>
Spiral arms are the regions in stars extending from the middle of spiral galaxies and the barred spiral. Those long, thin areas look like a spiral and therefore give their name to spiral galaxies.
Spiral arms, though, include many young, blue stars, that render their arms so bright (due to the high mass density and the fast stellar forming rates).
B.) crossing over, this is when chromosomes exchange DNA
The main structure, which distinguish the eukaryotic cells and the prokaryotic cells are the membrane bound organelles.
The eukaryotic cells are divided by the internal membrane. The internal membranes form the outer covering of the organelles. The organelles such as mitochondria, nucleus, Golgi apparatus, endoplasmic reticulum etc are absent in the eukaryotic cells.
Parasympathetic nerves govern involuntary actions such as pupil dilation, peristalsis, gland secretions, etc.
C. Diffusion.
The particles move WITH the concentration gradient
