【单选题】

An “emergency” however, almost always involves a failure that requires immediate and rapid response, such as a total powerplant failure, fire or smoke, or rapid cabin decompression.

A、However, an “emergency” almost always entails a failure that requires to respond immediately and rapidly, for example, the situations that a total powerplant fails, the fire or smoke occurs, or the cabin are depressurized rapidly.
B、An “emergency” however, almost always causes a malfunction that requests immediate and rapid response, such as the whole powerplant failure, fire or smoke, or rapid cabin pressurization.
C、However, an “emergency” is often related to a failure that demands respond simultaneously, such as the complete failure of the powerplant, fire or smoke, or rapid cabin warming.