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

• A

  $∆\mathrm{U}=-∆\mathrm{W}$,in an isothermal process

• B

  $∆\mathrm{U}=-∆\mathrm{W},$in an adiabatic process

• C

  $∆\mathrm{U}=∆\mathrm{W},$in an isothermal process

• D

  $∆\mathrm{U}=∆\mathrm{W},$in an adiabatic process