Bridge-head hydrogen of the conformer of cis-decalin is positioned as [a = axial; e = equatorial] A. a, a B. e, e C. a, e D. pseudo-a, pseudo-e

Option B is incorrect because both bridge-head hydrogens would be in equatorial positions. This would make the molecule less strained, but it is still not a stable conformation.

Option D is incorrect because the bridge-head hydrogens are not in pseudo-axial or pseudo-equatorial positions. These are special positions that are not axial or equatorial, but are in between. They are not stable positions for the bridge-head hydrogens in cis-decalin.