What type of lines provide an internal view of the object on a blueprint?

The correct answer highlights the role of cutting-plane and section lines in providing internal views of objects on a blueprint. These lines are essential in technical drawings because they represent a hypothetical cut through the object to expose its interior features. When a cutting-plane line is drawn, it indicates where the view is taken, and the corresponding section view that follows reveals the internal layout, structural components, and other details that are otherwise obscured in the exterior view.

By using cutting-plane and section lines, designers and engineers can convey complex internal features, allowing for more comprehensive understanding and analysis of the object. This is particularly important in fields such as architecture and mechanical engineering, where recognizing the internal arrangements is crucial for functionality and construction.

In contrast, leader lines are used to designate annotations or reference points, centerlines indicate the axis of symmetry, and extension lines show the dimensions of features but do not provide internal views of the object. These serve different purposes in a blueprint, which underscores the specific role that cutting-plane and section lines play in revealing internal details.