Question

A straight line parallel to the $x$-axis has equation _____.

• A. $x=a$
• B. $r=a$
• C. $y=x$
• D. $y=c$

Answer 1

The correct option is D $y=c$

The above figure is self explanatory,

Any line parallel to $x$ axis has a constant $y$-intercept and no x-intercept, thus it will have equation.

$y=c$ (also note that slope $=0$, so the term $mx$ disappered from general equation $y=mx+c$.