Answer: The answer is a. biotic.
Explanation: Biotic factors are living things in an ecosystem. Abiotic factors are non-living things in an ecosystem.
Examples of biotic factors include:
Plants
Animals
Bacteria
Fungi
Protists
Dead organisms
Examples of abiotic factors include:
Sunlight
Water
Soil
Air
Temperature
pH
Therefore, things that are alive, or were alive at some time, are biotic factors.
Have a good day; I hope this helps!