Final answer:
Contrasting lines that are horizontal and vertical form a hard edge at the point of intersection, creating a 90-degree angle. This is one of the basic principles in geometry.
Therefore, option C is present.
Step-by-step explanation:
When contrasting lines are described as horizontal and vertical lines that create a hard edge, they form a specific angle where they meet. This type of intersection is known in geometry for its unique property of creating right angles. A right angle is exactly 90 degrees, meaning that the lines are perpendicular to one another. This is a fundamental concept in geometry often observed in various real-world structures like buildings and it is crucial to many engineering and architectural designs.
Regarding the options provided in the question, when horizontal and vertical lines intersect, they do not form a 30-degree angle, a 45-degree angle, or a curved arc. They specifically form a 90-degree angle.
Therefore, the correct answer to the question "Contrasting lines are horizontal and vertical lines that create a hard edge and form what angle?" is c. a 90-degree angle.