[单选题]
If you walk 5.0 m horizoqi7ck3qs yu*6ww cd,z1jf:1 y ntally feb2jjqfr8w ;6 orward at a constant velocity carrying a 10-N object, the amount of wowrej2f6 b8;jqrk you do is
A. more than 50 J.
B. equal to 50 J.
C. less than 50 J, but more than 0 J.
D. zero.
