Question

what could cause a species to go extinct?
a new food source exclusive to this species
the introduction of new alleles into a population
when a species is unable to keep up with changes in the environment

Explanation:

When a species can't adapt to environmental changes (like climate shifts, habitat loss, or new predators), it struggles to survive. A new exclusive food source would help the species (more resources), and new alleles (genetic variations) can introduce beneficial traits. But inability to keep up with environmental changes directly threatens survival.

Answer:

when a species is unable to keep up with changes in the environment