Question 159700
 can someone help me with this question: 
Which common graph represents a horizontal line? 
a. The constant function
b. The identity function
c. The inverse function
d. None of the above, horizontal lines are not functions
---------------------------
a. The constant function.  It's called 'constant' because the value of y is a constant.
y = 2 is a horizontal line 2 units above the x-axis, parallel to the x-axis.