B. Protistans, a group thought to have given rise to other eukaryotic cells
<h2>540 million years ago
</h2>
Paleozoic.
Era immediately follows Precambrian It lasted about 4.5 billion years.
When did abundant fossil evidence first appear in the geologic record.
540 million years ago.

Work done = 100J
Distance = 5 meters
Force = ?

Force = 100/5 = 20N
Therefore, the force needed is 20 Newtons