Answer :
If any arbitrary surface encloses a dipole, the net charge is zero.
Dipole consists of two equal and opposite charges.
$E= \large\frac{1}{4 \pi \in_0}.\frac{q}{r^2}$
q is the charge , r is the distance from the charge .
$q=0$
$E= 0$
Electric flux $\Delta \phi =E. \Delta S$
$\therefore \Delta \phi =0$