Answer
B
Work Step by Step
In examining the cladogram, we look at the characteristic that arose before any of those species arose.
Option A is incorrect. The placenta arose right before the evolution of humans.
Option C is incorrect. Four limbs evolved after the appearance of the trout.
Option D is incorrect. Mammary glands appeared right before the appearance of the wallaby and human.
Option B is correct. The notochord appeared before the appearance of the trout, wallaby, and human; this means that these species share this characteristic.
