Koala bears are a specialist species because they a. only eat eucalyptus leaves b. are marsupials c. live in trees d.

The right option is; only eat eucalyptus leaves

Koala Bears are a specialist species because they only eat eucalyptus leaves.

Specialist species are species that can survive only in a limited range of conditions such as diet, camouflage, climate etc. Koala bears are marsupial mammals that feed selectively on the leaves of eucalyptus trees. The nutrient content of the diet (eucalyptus leaves) is very poor, and provides the organisms little amount of energy. Specialist species such as the koala bears are very bad at competing with other organisms, and are much more likely to go extinct when the specific conditions change.

only eat eucalyptus leaves

substitution is the answer in this case