Which cells are the exception to the rule that the cells of a leaf epidermis contain no chloroplasts?

Explanation

Almost every cell of the surface layer of a leaf lacks chloroplasts, and the pair of cells flanking each pore is the single exception to that pattern: those two are differently equipped because they have a different job, working the pore between them, while the rest of the layer only covers the leaf. Students who learn the rule as a flat statement about the whole surface layer then deny the exception, and the column-shaped cells beneath the surface are not part of that layer at all.