41. 如右圖所示,薄壁管斷面壁厚皆為6 mm,承受一 扭矩T=4 KN–m作用,試求壁中剪應力大小為何?(A) 32.83 MPa(B) 65.67 MPa(C) 98.5 MPa(D) 131.32 MPa