1. I think it's the trails left by an electron as it moves around the nucleus.
2. The atomic number is the number of protons so it is 8.
3. It's mass is lowered but it is still the same element.
Answer:
Explanation:
Given
mass of spring 
extension in spring 
downward velocity 
Position in undamped free vibration is given by
where 
also 
it is given
substituting values we get
Cumulonimbus clouds are associated by severe weather. They are thunderstorm clouds that bring heavy rain, snow, hail, lightning and even tornadoes.
Let's start with an infinitive: it has a form "to..." - only sentences C and D have a phrase like this, so we can exclude other options.
Among those, C does not have a gerund, which is a verbal form: "dreaming" has a function of a noun there.
So the correct answer is the remaining one, D.
