Answer:

Explanation:
Let assume that ball begins its movement at a height of zero. The height can be found by energy approach, to be precise, by Principle of Energy Conservation:


Answer:
b. the Paleozoic Era
Explanation:
The first vertebrates to appear are primitive fish in the Cambrian Period, but bony fishes with actual bony vertebratae didn't appear for another 100 million years. The Cambrian Period is the first of three periods in the Paleozoic Era. The Cambrian explosion was an event when practically all major animal phyla started appearing in the fossil record.
<u>Answer:</u>
<em>Construction of a railroad route is a strenuous task and one has to face several obstacles.
</em>
<u>Explanation:</u>
Setting up the best possible plan for laying a rail route is a time-taking task. Several factors like economical nature of the plan, proper availability of building materials, minimum river crossings etc should be considered.
To build a railroad route the government has to get hold of the land through which the railroad route is planned. This is never an easy task. The people of the area have to be given adequate compensation and should be properly evacuated. The chances of people disapproving the plan are more.