Which scenario would cause a covalent bond to form?

Searching for this question, I found the options on the internet.
"1.Two atoms share electrons so they can fill their outer shells2.The constant motion of electrons and the creation of charge imbalances bonds two molecules together3.A hydrogen atom with a slight positive charge is attracted to a negative charge of another molecule or atom4.One atom loses one or more electrons and the other atom gains one or more electrons"

The correct answer would be number 1. A covalent bond is achieved when two atoms share electrons from their outer shell so that they have a full outer shell leading to the electronic configuration balance they need.

Determine the  wavelength of light emitted when an electron  in an li2+ ion  makes a transition from an orbital with n  =  6 to an orbital with n  = 5.