A. S waves are also called secondary waves
B, both in real history and this chart, America created the first atomic weapons, and Russian spies during WW2 wanted to have the advantage of such power, lest America have a monopoly on pure Force.
<span />
The beginning of the Precambrian<span> period starts with the formation of Earth about 4.5 billion years ago and ends at the first sign of complex life about 540 million years ago. Though the </span>Precambrian<span> Period is often referred to as a period, it's actually the only supereon, which means that it spans multiple eons. The Precambrian is known as the geologic era. The Precambrian is the 1st era. hope that helped</span>
