Can somebody me figure this out? i think the answer is d

in this diagram, which equation could you prove to be true in order to conclude that the lines are parallel?

−ab=−cd

−ab⋅−dc=−1

−ab⋅−cd=−1

−ab=−dc

For two lines to be parallel, their slope must be the same.
To find the slope, we can use the form:

For the top line, the change in height (y value) can be seen as a - 0 or simply a, and the change in base is just -b (because our is just 0, from the origin.

Hence, line 1's gradient is:

Now, we can repeat this process for line 2:
Change in height is -d, change in base is c

Hence, line 2's gradient is:

For the two lines to be parallel, both gradients must be the same: 

2,4,5,8,10 are divisible by 40