What holds the atoms together in a covalent bond?
the attraction between the shared electrons and protons in each nucleus
a weak electron cloud
the attraction of the opposing ions
the crystal lattice structure

A.The attraction between the shared electron and the protons in each nucleus

Explanation:

Covalent bonds are formed when the atoms involved in bonding share their electron pairs.

When the atoms comes close to each other two types of forces acts on it:

1)Repulsive forces: electron-electron repulsion and nuclei-nuclei repulsion

(Similar charges repel each other,electrons are negatively charged and protons are positively charged)

2)Attractive forces: nuclei-electron attraction or

The attraction between the shared electron and the protons in each nucleus

A covalent bond is formed when the net force of attraction balances the net force of repulsion and the system acquire minimum energy.

indium, and thallium have three electrons i think