Construction sites use several temporary structures, each doing a distinct job, and this question checks if those jobs are matched correctly.
- Centering: this is the falsework built to hold the formwork of arches, domes, and other curved or spanning members in place while the concrete or masonry sets and gains strength. Read this way, the statement correctly captures what centering is used for.
- Scaffolding: this is the pipe-and-plank framework put up against a building so masons and other workers get a stable platform to stand, move, and store material on while they work at height. The statement matches this use directly.
- Shoring: this is a temporary prop or support fixed to an existing wall or structure so it does not collapse while nearby excavation, demolition, or repair is going on. Nothing about shoring deals with keeping water or moisture out of a building; that job belongs to damp-proof courses and waterproofing membranes, a separate part of construction altogether. So this statement is false.
- Underpinning: when an existing foundation is too weak or too shallow, builders work below it in small stages to add depth or width, which is underpinning. The statement's description, strengthening or deepening foundations, is exactly what underpinning does.
Three of the four descriptions, centering, scaffolding, and underpinning, correctly state what each temporary structure does, while the claim about shoring preventing dampness mixes up structural support with waterproofing, so it does not hold.
Let's summarize:
- Centering supports arch, dome, and slab formwork; scaffolding gives workers a platform; underpinning deepens or strengthens foundations, all correct.
- Shoring only gives temporary structural support; dampness is stopped separately by damp-proofing, so that statement is wrong.
So the correct statements are (A), (B), and (D).