Which synapomorphy finally allowed metazoans to leave an aqueous environment and inhabit land?

a.

limbs

b.

scales with keratin

c.

lobed fins

d.

the amniotic egg

e.

lungs

lungs

Explanation:

A new study, out today, suggests that the shift to lungs and limbs doesn’t tell the full story of these creatures’ transformation. As they emerged from the sea, they gained something perhaps more precious than oxygenated air: information. In air, eyes can see much farther than they can under water. The increased visual range provided an “informational zip line” that alerted the ancient animals to bountiful food sources near the shore, according to Malcolm MacIver, a neuroscientist and engineer at Northwestern University

the answer is 100% density i've answered this question before and done the quiz myself.