The single most important feature to consider when purchasing a scuba regulator is: How well it performs in controlled laboratory testing. A second-stage adjustment knob to ensure ease of breathing. The availability of regular, professional maintenance. Both the first and second answers are correct.

A diving regulator is a pressure regulator that reduces the pressure of gas in the tank and deliver it to the diver so that he/she can breathe easily. It must pass the controlled laboratory testing and must have a second adjustment knob to ensure ease of breathing. Modern regulators are precision made and designed to work under demanding conditions. 1st stage and 2nd stage, diaphragm and piston, exhaust valve and purge button are types of diving regulators.

i think the answer would d

the electromagnetic energy from the sun arrives in the form of visible and invisible light.