[单选题]
The work done on an ideal gas system in a aec 2.*p9hecdn isothermal process is -m d3ek lwy6n3v5e( t8huf.14lx*a hqp.d,mhf400 J. What is the change in internal hdlmnxw ..tdv8ulefahme6yh3 3f5k p4(* ,q 1energy?
A. zero
B. $-400 \; J$
C. $400 \; J$
D. none of the above
