43. 下列何者並非壓鑄鑄件氣孔產生之原因？ (A)壓鑄溫度低 (B)壓鑄溫度高 (C)壓鑄壓力大 (D)壓鑄產生亂流

3. A single closed loop of chain of mass m and length l rests on the surface of a smooth, frictionless cone. The chain lies in a horizontal plane. The half-angle of the cone is α. What's the tension in the chain?(A)\( T = \frac{mg}{\tan\alpha} \)(B)\( T = \frac{mg}{2\pi} \)(C)\( T = mg \)(D)\( T = \frac{mg}{2\pi\cot\alpha} \)(E)\( T = \frac{mg}{2\pi\tan\alpha} \)