[单选题]
A force moves an objtq.:: fsi zx5j/k:(ude8k nln ect in the direction of the for q;blj04x kv2uce. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 2.0 to 4.0 uvq b2x0lk;4 jm.
A. $20 \; J$
B. $40 \; J$
C. $60 \; J$
D. $80 \; J$
