In the NCh1619 standard, what is the appropriate period of time to estimate the duration of noise?

The duration of noise should be estimated in a suitable period of time chosen based on the specifications of the local authority.
For nocturnal noises, it may be advantageous to set an absolute limit for the noise level.
In our country, the relevant periods have been regulated as those between 7:00 and 21:00 h and from 21:00 to 7:00 h.
a) Only statement 1 is correct.
b) Statements 1 and 2 are correct.
c) Statements 1 and 3 are correct.
d) All statements are correct.