Answer and Explanation:
If we have a scaffold under construction, we will have an environment with some risks that must be combated, through guidelines that protect not only workers, but also people who are possibly passing through the site.
The construction of the scaffold leaves the environment dangerous because it can present risks of slips and debris falls, electrocution risk, risks of poorly prepared structure, among others.
The answer is that concession is a noun
The answer is c. He was tired and it was late; it had been a long day. The semi-colon helps distinguish the two separate parts. The part where it says "it had been a long day" doesn't make sense if added by a comma.