C and D are units of length or distance.
A is a measured angle.
B is a unit of angular measurement.
Answer- There are two reasons that we know quotations have been used first is the use of of name of the person who quoted it and secondly the quotation is written inside the quotation marks.
Explanation- Quotation is nothing but using a line that has been already quoted by someone somewhere. Such sentences are normally written inside quotation marks. In the above given paragraph the name of the person who quotes the sentence is also given hence we know that our quotation has been used.
Answer: Looked it up but
Explanation:
When the skater lands on the track, the vertical component of his kinetic energy is converted to thermal energy. You can do experiments where there is no loss to thermal energy (only PE and KE conversions) by turning friction off and by making sure the skater doesn't leave the track.
Answer:

Generally given that the electric field is negative it mean that its direction is opposite to that of the force
Explanation:
From the question we are told that
The charge on the small object is 
The force is 
Generally the magnitude of the electric field is mathematically represented as

=> 
=> 
Generally given that the electric field is negative it mean that its direction is opposite to that of the force