It is given that the system is assumed to be in steady circular motion with constant angular velocity ω. We know that L=m(r×v) where, L= angular momentum, v= velocity of the particle, m= mass of the particle and r= radius of the circular path traced by the particle. Since, LA is the angular momentum of M about point A which lies in positive z-direction. Therefore, with respect to point A, we will get the direction of L along positive Z-axis and of constant magnitude of mvr. Since, LB is the angular momentum of M about point B, so with respect to point B, we will get the constant magnitude of L but its direction will be continuously changing. Hence, option (d) is correct.