Fluorine
Check out the periodic table. Exact mass number of Fluorine should appear as 18.99...
        
             
        
        
        
Power is measure in watts which is joules per second
        
             
        
        
        
Answer:
C. It will increase in size.
Explanation:
 
        
             
        
        
        
Answer:
A. 14.59
Explanation:
Firstly, rounding a number means making a number simpler but keeping its value close. So rounding 14.587020 means making it look less complex but making sure the rounded value is within range of the original value.
Next, we have to know that to round a number;
* Digits below 5 (<5) rounds down the next digit to their left i.e. we leave the digits the same and turn the rounding digit to 0.
* Digits above 5 (>5) rounds up the next digit to the left i.e. we add 1 to the next digit
Next, to round to 4 significant digits means we want to see only the first four non-zero digits in our value. Note that, all non-zero digits i.e. 1-9 are significant
Hence, 14.587020 will be:
= 14.587020
= 14.58700
= 14.59000
 
We have four (4) digits which are non-zero already, hence we stop here and remove all zeros to the right
Hence, 14.587020 to 4 significant digits is 14.59 i.e. 14.587020 ~ 14.59