[单选题]
The work done on an +.2u6qcsd2t 7g elgmn ie h(1 8ek0vd2tplwrp9o okp 1jbit:7;deal gas system in an isothermal process is -400 J. What is the change ivpert: 07kj2 w9 idke11o;p 8pb(h toln internal energy?
A. zero
B. $-400 \; J$
C. $400 \; J$
D. none of the above
