[单选题]
If you push twice as x-.y6-hh*a21imn c jn/rlebn har ah0io(t (cn49 af,uvad against a stationary brick wall, the amount of work you do(fh0t a v(9noaicau,4
A. doubles.
B. is cut in half.
C. remains constant but non-zero.
D. remains constant at zero.
