[单选题]
In the Atwood machine show+)kjhq;u.7 wbgosnef/t+su d *kxy .8n in Fig. 4-1, if M = 0.60 kg and m = 0.40 kg 9fx /n4kwk(qz, what is thznx49fwk( qk /e magnitude of the acceleration of the system? (Ignore friction and the mass of the pulley.)
A. $5.3 \; m/s^2$
B. $3.9 \; m/s^2$
C. $2.0 \; m/s^2$
D. $0.98 \; m/s^2$
