Explanation:
Hybridization is the process of combining atomic orbitals to form hybrid orbitals that have different properties than the original orbitals. The central atom in a molecule/ion is the one that forms the most number of bonds. The hybridization of the central atom determines the shape and geometry of the molecule/ion.

The four types of hybridization are: sp, sp2, sp3, and sp3d. In sp hybridization, one s and one p orbital combine to form two hybrid orbitals. In sp2 hybridization, one s and two p orbitals combine to form three hybrid orbitals. In sp3 hybridization, one s and three p orbitals combine to form four hybrid orbitals. In sp3d hybridization, one s, three p, and one d orbital combine to form five hybrid orbitals.

To determine the hybridization of the central atom, we need to count the number of sigma bonds and lone pairs of electrons around it. The hybridization is then determined as follows:

- For 2 sigma bonds and 0 lone pairs, the hybridization is sp.
- For 3 sigma bonds and 0 lone pairs, the hybridization is sp2.
- For 4 sigma bonds and 0 lone pairs, the hybridization is sp3.
- For 5 sigma bonds and 0 lone pairs, the hybridization is sp3d.

Now, let's look at the given options:

a) NO2- and NH3:
- In NO2-, the central atom is N and it has 3 sigma bonds and 1 lone pair of electrons.
- In NH3, the central atom is N and it has 3 sigma bonds and 1 lone pair of electrons.
- Both have sp3 hybridization.

b) BF3 and NO2-:
- In BF3, the central atom is B and it has 3 sigma bonds and 0 lone pairs of electrons.
- In NO2-, the central atom is N and it has 2 sigma bonds and 1 lone pair of electrons.
- BF3 has sp2 hybridization and NO2- has sp3 hybridization.

c) NH2- and H2O:
- In NH2-, the central atom is N and it has 2 sigma bonds and 1 lone pair of electrons.
- In H2O, the central atom is O and it has 2 sigma bonds and 2 lone pairs of electrons.
- NH2- has sp2 hybridization and H2O has sp3 hybridization.

d) BF3 and NH2-:
- Same as option (b).
- BF3 has sp2 hybridization and NH2- has sp2 hybridization.

Therefore, the correct answer is option (b) - BF3 and NO2-.