A driving wheel and three driven wheels are installed in the transmission shaft with a diameter of D shown. The torques m 1 =15 KN × m , m 2 =2 KN × m , m 3 =8 KN × m, m 4 =5 KN × m are exerted on the four wheels, and the four wheels must be mounted on the four sections of A, B, C, and D . Considering the strength and stiffness of the shaft, the most reasonable layout of the wheel is ___. 1 2 3 4