【单选题】

临界迎角是液体或气流从表面开始分离，导致流体效率降低的角度。临界迎角是设计空气动力学表面时的重要考虑因素，例如飞机机翼、涡轮叶片等，因为它决定着不会导致升力或推力损失的最大攻角大小。

A、Crucial angle of attack is the angle at which a stream or air flow begins to split from a surface,causing a decrease in efficiency. It is important for designing dynamic surfaces ,such as airplane wings,turbine blades,as it determines the maximum attack angle that can be achieved without causing loss of lift or thrust.
B、Crutial angle of attack is the angle at which a stream or air flow begins to seperate from a surface,causing a decrease in efficiency. It is important for designing aerodynamic surfaces ,such as airplane airfoils,turbine blades,as it determines the maximum attack angle that can be achieved without causing loss of lift or thrust.
C、Critical angle of attack is the angle at which a fluid or air flow begins to separate from a surface, causing a reduction in the efficiency of the flow. The critical attack angle is an important consideration in the design of aerodynamic surfaces, such as airplane wings, turbine blades, as it determines the maximum angle of attack that can be achieved without causing a loss of lift or propulsion.