1. Consider a linear triatomic molecule H-A-H, where A is some
arbitrary other atom. How do you think can the MOs be labeled in
this molecule?
(A) With n and . There is no symmetry label available, because we are dealing with a heteroatomic molecule.
(B) With n,  and a “u” or “g” symmetry subscript. The molecule itself has
inversion symmetry, and this symmetry translates into even or odd inversion symmetry of the MOs as well.
(C) Only with n. There is more than one internuclear axis, so  is not
conserved either.

2. Consider a linear triatomic molecule H-A-H, where A is some
arbitrary other atom. How do you think can the MOs be labeled in
this molecule?
(A) With n and . There is no symmetry label available, because we are dealing with a heteroatomic molecule.
(B) With n,  and a “u” or “g” symmetry subscript. The molecule itself
has inversion symmetry, and this symmetry translates
into even or odd inversion symmetry of the MOs as well.
(C) Only with n. There is more than one internuclear axis, so  is not
conserved either.

3. The sp3 hybrid functions shown here
are not all possible combinations
(8 combinations are possible).
Do the others exist?
(A) No, because they are not allowed.
(B) Yes, but they are identical to the others
and therefore not shown.
(C) Yes, but they are the result of a symmetry
inversion on the C atom and the physics is
just the same.
(D) No, they would all point in the same direction,
which makes no chemical sense.

4. The sp3 hybrid functions shown here
are not all possible combinations
(8 combinations are possible).
Do the others exist?
(A) No, because they are not allowed.
Baloney!
(B) Yes, but they are identical to the others
and therefore not shown.
Not identical! See (C)
(C) Yes, but they are the result of a symmetry
inversion on the C atom and the physics is
just the same.
(D) No, they would all point in the same direction,
which makes no chemical sense.