What human stance was reintroduced in art made in Italy during
the 15th century?

Contrapposto - an asymmetrical arrangement of the human figure in which the line of the arms and shoulders contrasts with, while balancing, those of the hips and legs.

Explanation: Donatello carved statues for Or San Michele's niche Saint Mark. He incorporated Greco-Roman sculptural principles, executed for the guild of linen makers and tailors. He depicted motion in the human figure by recognizing the principle of weight and shift (contrapposto.) He reintroduced this concept of contrapposto into Renaissance statuary. His Saint Mark is the first Renaissance statue whose robe accentuates the movement of his figure.