Four.
2
Mammals have 4-chambered hearts and one pair (2 total) of lungs.
Four chambers.
4 chambers as they are mammals.
The design of the mammalian heat is that there are two chambers used to receive blood from, and pump blood to the lungs, and then two more chambers used to received blood from, and pump blood to the rest of the body other than the lungs. This arrangement works more efficiently than if there are only two chambers receiving blood from and pumping blood to the entire body including the lungs.
mammals have 4.
All mammals have a four-chambered heart.
16 16
Like all mammals, the kangaroo's heart has four chambers.
4
A mammalian heart has four chambers and they are right and left atrium and right and left ventricle.
The platypus has two lungs, like all mammals do.
The heart of fish have two chambers. The heart of reptiles and amphibians have three chambers. The heart of mammals have four chambers.