Q: Describe the stages of development in a multicellular organism that is familiar to you.

Humans:

To put it simply, a human starts as a fetus, then they are born..so that's a baby, then they hit 2 years old and are considered toddlers, once they turn 5-6, they start kindergarten, so we no longer refer to them as toddlers, they are children, when they hit 13 we call them pre-teens, once they hit 15-16 we call them teens, 21-25 they are young adults, 25 up until 50's they are adults, once they hit 50-60 they are seniors.

Explanation:

i am going to guess that it is co2.