The answer is C.
It is C because Slope is the change in y over the change in x. From point 1, -4 it rose 6 and ran 2 which simplifies to 3. (If you know the rise over run thing you will understand what I mean. BUT THE LINE IS GONG DOWN SO THE SLOPE IS NEGATIVE!)
Also -1 is the y-intercept because it crossed over the y axis, so A is already incorrect. D is incorrect because the slope is positive. And C is, well just wrong.
Hope this helps:)
