**Explanation:**

The transition elements are defined as the elements that have partially filled d orbitals in their ground state or in any of their oxidation states. These elements typically exhibit a wide range of oxidation states and form coordination compounds due to the presence of empty d orbitals.

Let's analyze each group of elements given in the options:

**a) Sc, Y, La**

- Scandium (Sc), Yttrium (Y), and Lanthanum (La) are all considered transition elements.
- Scandium has the electron configuration [Ar] 3d1 4s2, with one electron in the d orbital.
- Yttrium has the electron configuration [Kr] 4d1 5s2, with one electron in the d orbital.
- Lanthanum has the electron configuration [Xe] 5d1 6s2, with one electron in the d orbital.
- Therefore, this group of elements is regarded as transition elements.

**b) Cu, Ag, Au**

- Copper (Cu), Silver (Ag), and Gold (Au) are all regarded as transition elements.
- Copper has the electron configuration [Ar] 3d10 4s1, with partially filled d orbitals.
- Silver has the electron configuration [Kr] 4d10 5s1, with partially filled d orbitals.
- Gold has the electron configuration [Xe] 4f14 5d10 6s1, with partially filled d orbitals.
- Therefore, this group of elements is regarded as transition elements.

**c) Zn, Cd, Hg**

- Zinc (Zn), Cadmium (Cd), and Mercury (Hg) are not regarded as transition elements.
- Zinc has the electron configuration [Ar] 3d10 4s2, with completely filled d orbitals.
- Cadmium has the electron configuration [Kr] 4d10 5s2, with completely filled d orbitals.
- Mercury has the electron configuration [Xe] 4f14 5d10 6s2, with completely filled d orbitals.
- These elements do not have any partially filled d orbitals in their ground state or in any of their oxidation states, so they are not considered transition elements.

**d) Cr, Mo, W**

- Chromium (Cr), Molybdenum (Mo), and Tungsten (W) are all regarded as transition elements.
- Chromium has the electron configuration [Ar] 3d5 4s1, with partially filled d orbitals.
- Molybdenum has the electron configuration [Kr] 4d5 5s1, with partially filled d orbitals.
- Tungsten has the electron configuration [Xe] 4f14 5d4 6s2, with partially filled d orbitals.
- Therefore, this group of elements is regarded as transition elements.

Based on the analysis above, the correct answer is option 'c': Zn, Cd, Hg. These elements do not have partially filled d orbitals and are not regarded as transition elements.