Which of these is a biotic factor of an aquarium ecosystem?

a: algae growing on the glass
b: gravel on the bottom of the aquarium
c: temperature of the water
d: amount of oxygen in the water

The answer is A:algae growing on the glass. A Biotic Factor is any living thing in a ecosystem and a Abiotic is any non-living things like
B:gravel on the bottom of the aquarium
C:temperature of the water
D:amount of oxygen in the water

I would say A) ALGAE because gravel is abiotic and so is gravel and oxygen and temperature

Dissociation then hydration dissolving

You would do 1500/4 and the answer is 375