The correct answer is B) sufficient oxygen in a compartment to support life. An oxygen indicator is used to measure the oxygen content in a given space or compartment. This is important to ensure there is adequate oxygen to support human life and prevent hazardous conditions such as asphyxiation. The indicator can determine if the oxygen level is within the safe range, typically between 19.5% and 23.5% by volume. It does not detect the presence of hydrogen gas or combustible gases, which are measured by different types of gas detectors.