A regulator equipped with a conventional alternate-air-source second stage:________ a) Is the among the most widely used and readily understood type of alternate air source. b) Limits the receiver to using only the alternate-air-source second stage. c) Allows the donor to give either second stage to an out-of-air diver. d) Both the first and third answers are correct.

A regulator equipped with a conventional alternate-air-source second stage is among the most widely used and readily understood type of alternate air source, and allows the donor to give either second stage to an out-of-air diver. d) Both the first and third answers are correct.

Here we are talking about scuba diving equipment. It is the regulator that allows the diver to breathe from the oxygen tank. It is of the utmost importance because the function of this piece of equipment is precisely to regulate the pressure of the air so the diver has no problems breathing while it is diving. Let's have in mind that the air contained in the oxygen tank is at high pressure. Without the regulator, it could be difficult for the diver to breathe and could put it at risk.