Chemical reactions cannot be observed directly because molecules are too small to be seen using your eyes or a microscope. Scientists use evidence to infer that a chemical reaction has occurred. Which evidence does not indicate that a chemical reaction has occurred?​

the correct answer is - ability to find a mate

the cladogram shown here shows similarities and differences among several classes of vertebrates. anatomically, the four have limb structure as their common ancestor. we might separate the mammals from the other three classes because they a) divergent; do not lay eggs b) identical; are warm-blooded c) varied; a four chambered heart d) homologous; have mammary glands

it is either c or d and i know for sure it is not a or b