Which of these are common to all mammals?

a: type of reproductive system, brain size, skin
b: digestive system, heart lungs
c: digestive system, number of toes, blood
d: kidneys, liver, skeletal structure

Answer is B

Explanation:

All of the other ones are either for humans or other things not common to all species

i think it is true since you can test the answer and can use observations to complete it.

shield volcanos are angry and get mad over the smallest things so much that there heads erupt   pahoehoe and a'a lava. a composite volcano is the poller opposite of a shield volcano. its   peaceful thing and knows how to control its emotions.