Koalas are marsupials that are found in eastern Australia. Although their ancestors lived mostly on the ground, modern koalas spend most of their time in eucalyptus trees. This is possible because their hands and feet have
strong claws and opposable digits.
What other adaptation could have helped koalas as they evolved from land dwellers to tree dwellers?

Fur color that closely matches the eucalyptus bark color

Explanation:

In terms of evolving from land dwellers to tree dwellers, the number of offspring does not matter. Although the ability to run faster is a good evolution for escaping predators, it does not help the koalas evolve to be better tree dwellers (how would you run using only the trees?). Communicating with their peers would be convenient for survival, but it does not help koalas become better tree dwellers. What does help koalas survive better by traveling through the trees is camouflaging with the bark of the tree to hide from predators.

an individual’s sex (i.e., whether they are a male or female) is determined by the sex chromosomes. most people have two sex chromosomes, one that is inherited from their mother and one that is inherited from their father. typically, females have two x chromosomes (xx) and males have one x chromosome and one y chromosome (xy). conditions caused by changes (“mutations”) in genes located on the x chromosome are considered x-linked.

x-linked recessive inheritance

most x-linked conditions are recessive. this means that in a person with two x chromosomes (most females), both copies of a gene (i.e., one on each x chromosome) must have a change or mutation whereas in a person with one x chromosome (most males), only one copy of a gene must have a mutation. a female with a mutation in one copy of a gene on the x chromosome is said to be a “carrier” for an x-linked condition. a male with a mutation in a gene on the x chromosome is typically affected with the condition. because females have two copies of the x chromosome and males have only one x chromosome, x-linked recessive diseases are more common among males than females. however, x-linked recessive diseases can occur in both males and females.

for x-linked recessive disorders, an unaffected carrier mother who has a mutation in a gene on the x chromosome can transmit either the x chromosome with this mutation or a “normal” x chromosome to her children. if the father is unaffected, none of her daughters will be affected and all of her daughters will be unaffected—since they will inherit at least one normal x chromosome from their father. however, each daughter will have a 50% chance of being an unaffected carrier like her mother and a 50% chance of both x chromosomes being normal.