[单选题]
In the Atwood machine shown in Fig.w (v7hvx g6k3k 4-1, ic r ,vzhi+ +:bz)5f; sqfvy*fjf M = 0.60 kg and m = 0.40 kg, what is the tension in the string? (Igno)bzy fc+ i +;v5srj:f*,zh fvqre friction and the mass of the pulley.)
A. $3.1 \; N$
B. $4.7 \; N$
C. $7.1 \; N$
D. $7.5 \; N$
