4.1 6th edition

[Lina Petrossian 1D]

4.1 Below are ball-and-stick models of two molecules. In each case, indicate whether there must be, may be, or cannot be one or more lone pairs of electrons on the central atom.

Could someone explain how they solved this?

[Joon Chang 2F]

a) Must have lone pairs of electrons because in order to have the bent shape, there must be one or more lone pairs contributing to the repulsion of the other atoms.
b) May have lone pairs. The linear shape could have zero lone pairs or multiple lone pairs all in the same axial plane.