During adiabatic expansion of an ideal gas, $100\mathrm{ }\mathrm{J}$ work is done, $\Delta \mathrm{E}$ of system is

- The expression for adiabatic expansion of ideal gas is

- $\Delta \mathrm{E}=\mathrm{q}-\mathrm{W}$, but given process is adiabatic in which heat is constant

- Therefore $\Delta E=0-W$,

- $\Delta \mathrm{E}=-W$, substituting the value of work we get $\Delta \mathrm{E}$

- $\Delta E=-100 \mathrm{J}$

Hence the correct option is (D).