To determine the correct labels for the components of the arch in the provided figure, we must understand the key architectural elements involved:

1. Extrados: The outer curve or surface of an arch. It is labeled as P in the diagram.
2. Key (or keystone): The central stone at the apex of an arch, locking the whole arch. It is labeled as Q.
3. Span: The horizontal distance between the supports of an arch. This is represented by R in the diagram.
4. Abutment: The part of an arch that bears the lateral thrust. In this diagram, it is shown as S.
5. Rise: The vertical distance from the springing line to the highest point of the intrados. It is marked as T.

Based on this understanding, let's match the labels:

• P – Extrados is correct.
• Q – Key is correct.
• R – Span is correct.
• S – Abutment is correct.
• T – Rise is correct.

The correct options that align with these explanations are:

• P – Extrados, Q – Key, R – Span
• Q – Key, S – Abutment, T – Rise