Which of the following species is neither hypervalent nor hypovalent ?

A molecule or ion is:

• Hypervalent: When the central atom has more electrons in its valence shell than an octet (e.g., PF₅, SF₆).
• Hypovalent: When the central atom has fewer electrons in its valence shell than an octet (e.g., BF₃, BeCl₂).
• A species that is neither hypervalent nor hypovalent has exactly 8 electrons in its valence shell, following the octet rule strictly (e.g., CH₄, NH₃, H₂O).