Which Feature of Some Carinates Has the Same Effect on Weight

Question

Which feature of some carinates has the same effect on weight as the presence of air sacs?
A) presence of a large, heavily keratinized beak
B) absence of a urinary bladder
C) presence of a carina (keel)
D) number of chambers in the heart
E) presence of large pectoral muscles

Accepted Answer

The absence of a urinary bladder in some carinates reduces their overall body weight, similar to how the presence of air sacs, which are lightweight and reduce the density of the bird, also contributes to a lighter body weight for flight.