Which of the following two elements will likely form a covalent bond? N and O K and Cl Li and F Na and Sr

Covalent bonds are also called molecular bonds. These chemical bondings involves atoms sharing electron pairs. Covalent bonding usually happen between 2 non-metals. Non metals are usually found in the left and right most sides of the periodic table. Hence, the answer will be A. N and O since both elements are non-metals.