Answer:
A. evaporation
Explanation:
Evaporation is a surface phenomenon as the molecules of the surface gets sufficient energy to overcome the force of attraction which will help in converting to the vapor phase.
Answer:
The first part can be solved via conservation of energy.

For the second part,
the free body diagram of the car should be as follows:
- weight in the downwards direction
- normal force of the track to the car in the downwards direction
The total force should be equal to the centripetal force by Newton's Second Law.

where
because we are looking for the case where the car loses contact.

Now we know the minimum velocity that the car should have. Using the energy conservation found in the first part, we can calculate the minimum height.

Explanation:
The point that might confuse you in this question is the direction of the normal force at the top of the loop.
We usually use the normal force opposite to the weight. However, normal force is the force that the road exerts on us. Imagine that the car goes through the loop very very fast. Its tires will feel a great amount of normal force, if its velocity is quite high. By the same logic, if its velocity is too low, it might not feel a normal force at all, which means losing contact with the track.
Answer:
The most abundant gas in Earth’s atmosphere is nitrogen, followed by oxygen, which is needed to burn wood and fuel. The third-most abundant gas is argon. The amount of carbon dioxide in the atmosphere is very small, making up just 0.33% of the atmosphere, but it is very important because plants use it to make simple sugars. Another important gas is water vapor, which condenses around small particles in the atmosphere to form clouds and then rain.
Explanation: