Answer: systematic random sampling
Step-by-step explanation:
Answer is a because -1 just means the opposite

Hope I helped, also, I used the math thingy, which I haven't used before, so I'm not sure quite how this turned out, well, I guess we will see in a minute! But if it does not work I can try it just typing regularly.
B as if you plug the co-ordinates into the equation and it equals 10: (3x4)-2= 12-2 =10
A doesn't work as the answer is 20
C doesn't work as the answer is 14
D doesn't work as the answer is -20