Homologous structures are: a) structures of animals that have the same appearances and functions but obviously no common ancestor. b) structures of animals that have different appearances and functions but different ancestors. c) structures of animals that have different appearances and functions but seem to have evolved from the same body part in a common ancestor. d) structures of animals that appear to have evolved from different parts of their bodies.

Answer is C.   Structures of animals that have different appearances and functions but seem to have evolved from the same body part in a common ancestor.

Explanation:

This can be found in Cat's leg and human arms.the structure do not need to look the same or perform the same functions.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation: