Which of the following is a true nut?

Nut is a fruit develops from polycarpellary, superior ovary. The pericarp is hard, woody or leathery, eg, edible part of chestnut is cotyledons. Ground nut is lomentum in which edible part is seed. Walnut is a drupe fruit in which edible part is cotyledon. Pistachio is a drupe in which edible part is seed.