What type of oxygen masks are used by the crew?

The correct choice indicates that the crew uses quick-donning and diluter demand oxygen masks. Quick-donning masks are purposefully designed to be donned quickly and easily in emergency situations, allowing crew members to maintain a high level of situational awareness and response efficiency. This is critical in aviation, where the ability to react promptly to cabin depressurization or other emergencies is essential for safety.

Diluter demand masks are designed to supply oxygen when the user inhales, mixing ambient air with the oxygen provided. This is advantageous because it conserves oxygen and can be used effectively at different altitudes. The combination of quick-donning capabilities with the efficiency of a diluter demand system makes this option highly effective for flight crew members.

In contrast, the other options either describe masks that do not incorporate quick-donning features or utilize systems that would not be as efficient or practical in a flight environment, where rapid response time and effective oxygen delivery are paramount.