2. This body system sends out scouts to recognize pathogens such as bacteria and viruses. Once identified, it produces antibodies to attack
and kill the pathogen. What body system is being described?
A-Immune
B-cardiovascular
C-muscular
D-digestive

a. A shared ancestral character.

Explanation:

The condition of birds and mammals having four limbs is a shared ancestral character because the structure of the limbs are similar in both the cases.

The forelimbs of the bird are modified into wings to aid flying.The hind limbs are modified into feel and claws.

These are homologous structures to the hands and feet in mammals.

That means they have a common origin, and hence are shared ancestral character.