[单选题]
The work done on an i:w -vy.v9 wn+chgph3cdeal gas sys3u: ea6z02 abafghy1qn.( i aetem in an isothermal process is -400 J. What isynqhf3eia6 u2 1a( :zaba0g.e the change in internal energy?
A. zero
B. $-400 \; J$
C. $400 \; J$
D. none of the above
