Answer:
A straight angle measures 180°. ... An angle can be measured using a protractor, and the angle of measure 90 degrees is called a right angle. In a right angle, the two arms are perpendicular to each other. When the right angle is divided into two equal parts each angle measures 45°.
1b exoshpere
2d change its form
Until the early Proterozic there were only negligible amounts of free oxygen in the atmosphere
