Answer: Option B) Common salt
Explanation:
An inorganic compound is one that does not contain carbon at all or contain carbon atoms that are not covalently bound to other atoms.
Hence, unlike kerosene, sugar and alcohol, common salt with the chemical formula NaCl has no carbon atoms, this will be regarded as an inorganic compound.
The answer is either A, the bottleneck effect or C, natural selection. The answer is most likely A because it is hinted that the predator fish was placed in the isolated stream. The predators eating the darters less than 5cm is natural selection though.