[单选题]
If you walk 5.0 m hori. f6wmy-gwqsb n:+w6vzontally forward at a constant velocity carryine2 um,u/nx ir;g a 10-N object, the amount of work you do is/ nr ei,muu2x;
A. more than 50 J.
B. equal to 50 J.
C. less than 50 J, but more than 0 J.
D. zero.
