Vertebrates share many physical characteristics. all vertebrates a. have an internal skeleton that includes a backbone or spinal column. b. have a thick exoskeleton but not an internal skeleton c. have neither an exoskeleton nor an internal skeleton. d. have an internal skeleton but not a backbone or spinal column.

A. All vertebrates have an internal skeleton that includes a backbone or spinal column.

Vertebrates are large, active animals and are known to be the most organized organism on earth. They are the most advanced group of animals with the presence of the vertebrae, spinal cord and notochords. Also, they have skeleton and muscles that enable them to move around efficiently.

enhanced global partnerships and exploration capabilities may advance international preparedness for protecting the earth from catastrophic events such as some asteroid strikes, advancing collaborative research on space weather and protecting spacecraft by developing new means for space debris removal.

the answer is d.) homologous; have mammary glands