An answer option that correctly completes statement 4 of the proof include the following: C. EH || FG.
What are parallel lines?
In Mathematics and Euclidean Geometry, parallel lines refers to two lines that are always the same distance apart and never meet.
This ultimately implies that, two (2) lines are parallel under the following conditions:
Slope of line 1, = Slope of line 2,
Based on the information provided about quadrilateral EFGH, we can logically deduce that it represents a square and as such, all of its sides have a slope of -1. Therefore, any parallel segment within it must have a slope of -1;
EF || GH (step 3)
EH || FG (step 4)