The correct answer is A. Ashlar arch.
An ashlar arch is an arch constructed with finely dressed stones. The stones are cut to precise shapes and sizes, and they are fitted together with great precision. Ashlar arches are often used in architecturally significant buildings, as they can create a very elegant and refined appearance.
A rubble arch is an arch constructed with irregularly shaped stones. The stones are not cut to precise shapes or sizes, and they are fitted together with less precision than ashlar arches. Rubble arches are often used in less important buildings, as they are less expensive to construct.
A gauged arch is an arch constructed with stones that are cut to specific shapes and sizes. The stones are fitted together with great precision, and the arch is then filled with mortar. Gauged arches are often used in buildings that require a high degree of structural strength, such as bridges and domes.
An axed arch is an arch constructed with stones that are cut with an axe. The stones are not cut to precise shapes or sizes, and they are fitted together with less precision than ashlar arches. Axed arches are often used in vernacular architecture, as they are a simple and inexpensive way to construct an arch.