Crown is located at A. Highest point on the extrados of the arch B. Highest point on the intrados of the arch C. Skew-back of the arch D. None of these

The correct answer is: A. Highest point on the extrados of the arch.

The extrados is the outer curve of an arch, while the intrados is the inner curve. The crown is the highest point on the extrados.

The skew-back is the back of the arch, where the two sides meet.

Here is a diagram of an arch, with the crown labeled:

The crown is the highest point on the arch, and it is located at the intersection of the two curves. The extrados is the outer curve of the arch, and the intrados is the inner curve. The skew-back is the back of the arch, where the two sides meet.