The correct option is C Adiabatic work
According to first law of thermodynamics,
ΔU=q+W=q−pΔV
In isochoric process (ΔV=0)
(ΔU=q)
In isobaric process (Δp=0)
(ΔU=q)
In adiabatic process (q = 0)
(ΔU=W)
In isothermal process (ΔT=0) and ΔU=0
∴ ΔU is equal to adiabatic work.