[单选题]
A force moves an object in thex,etvcpuvaj u o :7+y/7(h,pt direction of t(7 i4yf 4gp bee2l.ajuhe force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work4bl 7u (jf4eygap.e2i done when the object moves from 2.0 to 4.0 m.
A. $20 \; J$
B. $40 \; J$
C. $60 \; J$
D. $80 \; J$