The electronic configurations of the given elements are:
Eu (63): [Xe] 4f76s2
Gd (64): [Xe] 4f75d16s2
Dy (66): [Xe] 4f106s2
Ho (67): [Xe] 4f116s2
Tm (69): [Xe] 4f136s2
Yb (70): [Xe] 4f146s2
Lu (71): [Xe] 4f145d16s2
Hf (72): [Xe] 4f145d26s2
From the above configurations:
Eu and Gd both have 7 electrons in their 4f orbitals.
Yb and Hf both have 14 electrons in their 4f orbitals.
Dy and Ho have 10 and 11 electrons respectively in their 4f orbitals.
Lu and Tm have 14 and 13 electrons respectively in their 4f orbitals.
Thus, pairs A (Eu and Gd) and C (Yb and Hf) have the same number of electrons in their respective 4f orbitals.
Answer: A and C Only