(a) Oxygen and ethyne

(b) Carbon dioxide and ammonia

(c) Methane and ethane

(d) Nitrogen and ethyne

Solution:

Option (d) is the answer.

Nitrogen: Because each nitrogen atom requires three electrons to fill its outermost shell, nitrogen atoms will form three covalent bonds (also known as triple covalent) between two atoms of nitrogen.

Ethyne: The chemical ethyne (HCCH) is a linear one. There are no lone pairs of electrons on each carbon atom, which form two sigma bonds.