It would be the 3rd answer. Linear functions take on the equation
y = mx + b , m is the slope and b is the y intercept. That means in the equation given
m = 1/2 (slope) and b = -2 (y intercept)
The slope is rise over run or y/x so since the slope is 1/2 for every 1 unit moved up, you move 2 across. The y intercept is where the graph crosses the y axis.