Question

what is the advantage of concealed wiring?
a)easy to maintain
b)less voltage drop

c)high insulation resistance
d) protection against moisture​

Answer 1

The concealed wire is invisible, protected from possible damage like falling branches, but also difficult to get to in case of emergency. The reasons to hide it can be to protect it from damage requiring service, but if it receives damage regardless, the effort needed to service it has increased substantially.