Answer:
Ok, here we have two points A and B.
The shorter object will be the second option, AB with a line on top, this is a segment, so the length of this object is equal to the distance between A and B.
The next one is AB with an arrow pointing to the right, this is ray, is a line that starts in A and passes through B, and continues infinitely.
The third will be the bottom option, AB with a double-arrow on top, this is the notation for a line that passes through A and B, and it extends to infinity in both directions.
 
        
             
        
        
        
If you are taking the cm to km then it would be like this
4.5km*4.1cm= 18.45km