Planes Q and R intersect. Lines d and c are vertical on plane R and form a right angle with line B on plane Q. Line B is horizontal on plane Q. Line a is slightly diagonal on plane Q. In the diagram, the only figure that could be parallel to line c is

line a.
line b.
line d.
plane Q.

C. line d

Step-by-step explanation:

Two parallel lines are lines that do not meet even with continuous extension of their length. While two lines are perpendicular when they form a right angle to each other at the point where they meet.

In the given question, the only figure that would be parallel to line c is line d. Line a is not parallel to line c (since it is slightly diagonal, it would intersect line c at a point) and line B is perpendicular to line c (since it is horizontal to plane Q), same as plane Q. So that lines c and d are parallel to each other.