Elena agrees to finish a knitting project for a friend. The graph shows the number of rows Elena completes compared to the amount of time spent knitting. Assuming she worked at a constant rate, how many rows had been completed before Elena started working?

12
14
15
19

Which pairs of variables have a linear relationship? Select two options.

side length and perimeter of 1 face
perimeter of 1 face and area of 1 face
surface area and volume
area of 1 face and surface area
side length and volume