The correct answer is A: 2.
The slope compares the vertical change (the rise) to the horizontal change (the run) when moving from one fixed point to another along the line.
If you look at your graph, it takes 2 units up and 1 unit to the right in order to get to the next point on the line.
Therefore, the slope of the line is 2/1, or simply 2. It has a positive value because the line is sloping upward.