The avian cardiovascular system is able to quickly respond to changes in levels of activity (e.g., resting vs. flying) via changes in heart rate, cardiac output, & blood flow (by vasocontriction and vasodilation of vessels).
A square is a quadrilateral with all right angles and all equal sides. A square is also a parallelogram, a rectangle, and a rhombus and has all the properties of all these special quadrilaterals. Figure 3 shows a square. Figure 3 A square has four right angles and four equal sides. Figure 4 summarizes the relationships of these quadrilaterals to one another.
A parallelogram is a rectangle with each side that it's opposite to (or doesn't intersect with), parallel to the other, meaning that if the lines just continue and continue, they'll never intersect. A square is a parallelogram because the opposite sides, if you continue the line, they'll never touch each other.