If $\bigtriangleup U$ and $\bigtriangleup W$ represent the increase in internal energy and work done by the system respectively in a thermodynamical process, which of the following is true ?

Question

( A ) $\bigtriangleup U=\bigtriangleup W$, in a isothermal process
( B ) $\bigtriangleup U=-\bigtriangleup W$, in a isothermal process
( C ) $\bigtriangleup U=-\bigtriangleup W$, in a adiabatic process
( D ) $\bigtriangleup U=\bigtriangleup W$, in a adiabatic process