I'm pretty sure all 4 are subatomic particles but if i had to guess i'd be Photons
A cow's<span> digestive system is quite different from that of humans. </span>Cows eat grass, hay and other plant material that contain hard-to-digest<span> cellulose. To cope with this </span>they<span> have a large stomach with four compartments, with the largest being the rumen.</span>
Answer:

Explanation:
The number of valence electrons tells us the group number of the neutral atom.
The atom has 4 valence electrons.
The atom is in group 4.
The rock is limestone, I hope this helps!!