The only correct statement is Option D.
Reasoning:
Gauss's law in integral form reads
ΦE=∮E⋅dA=‌,where the surface integral is taken over a closed surface
S.
It holds for any closed surface, regardless of its shape or how the enclosed charge is distributed.
Open surfaces (Option A) aren't allowed because the "enclosed" concept only makes sense for closed surfaces.
Symmetry is not required for the validity of Gauss's law-it only makes field calculations easier (so Option B is false).
Charges outside the surface contribute zero net flux, but Gauss's law itself still applies (so Option C is false).
Hence:
Option D is correct.