Answer:The simplest methods of building design and construction have been used for thousands of years. Stacking stones, laying brick, or lashing wood together in one form or another are still used today in all parts of the world. However , over the centuries, innovations in methods and materials have given new expression to architecture and the human footprint on the landscape. We can also look to historical examples for clues that give context to different style periods.
Explanation: post and lintel was first discovered. With this, a system of posts –either stone or wood – are placed at intervals and spanned by beams at the tops. The load is distributed down the posts to allow for areas of open space between them. Its first use is seen at Stonehenge, a prehistoric monument in southern England dating to about 3000 BCE.
While the arch gave an alternative to lintel and post in the sense that
they supply strength and stability to walls without massive posts and beams because their construction minimizes the shear load imposed on them.
In conclusion, the vault is an extension of a arch in linear direction while the dome is formed when an arch rotated on its vertical axis.
By "equipment" here, I would assume that you are talking about gym equipment. While it is safe to try out a new equipment for as long as you practice caution and follow the instructions (a), it can probably damage your body in the end especially if you are following a weight program. If you are not careful, you might also damage the equipment and not just your body. So, in this case, I would say (c).
