Chapter 1 - Graphs - 1.3 Lines - 1.3 Assess Your Understanding - Page 30: 12

$(c)$

A graph where $y$ is equal to a constant will give you a graph where every $x$ value, be it 0 or 100, has the same $y$ value ($-3$ in this case) which creates a horizontal line at that y value. The y-intercept of the line $y=k$ is $k$. Thus, the answer is Option $(c)$.