Answer:
v = 5 m/s
Explanation:
Given that,
The distance covered by a runner, d = 400 m
Time, t = 80 sec
We need to find the runner's average speed. It is equal to total distance covered divided by time taken. It can be given by:

So, the runner’s average speed is 5 m/s.
Answer:
Mesozoic Era
Explanation:
The "Mesozoic Era" is divided into three periods: <em>Triassic, Jurassic and Cretaceous.</em> During the last period (Cretaceous), which was considered the longest, the extinction of reptiles occurred and the new mammals appeared. This event was also known as the "Cretaceous-Paleogene Extinction Event." Around <em>3/4 of plants and animals died</em>. Such event became significant boundary that laid between the Cenozoic Era and the Mesozoic Era. This made it significant in geologic history.
Answer:
E k Jejdjfjfjfjfjfjrjrek e l a
Replication from formation and separation of the strands