Two parallel lines has the same slope.
The given line:

Is written in the form y=mx+b where m is the slope.
The slope is 8
To find the parallel line you need to write the given options in the form y=mx+b by solving y, as follow:

Slope is -1/8 (it is not parallel to given line)
_______________

Slope is 1/8 (it is not parallel to given line)
________________

Slope is 8 (It is parallel to given line)
___________

Slope is -8 (it is not parallel to given line)
Then, as given line and line in option C have the same slope (8) they are parallel lines