Answer: The second description is correct for the absolute value of x
Main details: Horizontal line from 0 to the dot 6 ticks to the left, and 6 written above the line
Step-by-step explanation: breaking it down: 
A number line is shown from negative 6 to positive 6 with increments of 1. All the numbers are labeled on the number line. The first part is the same in all of the descriptions
A dot is shown on a point at 6 tick marks to the left of 0.  This represents -6 on the number line. 
Above the number line, a bracket is shown extending from a point at 6 tick marks to the left of zero to 0.  This shows the distance between 0 and -6. Important. Absolute value is the distance between two numbers
A horizontal line is shown between the brackets, This is the measuring line 6 units long.
 and 6 is written on the line.  Important. It is a plain number, no negative or positive! Absolute value is just that.