A hard-shelled fruit among the following is

A nut is a hard-shelled fruit of some plants having an indehiscent seed. Nuts are a composite of the seed and the fruit, where the fruit does not open to release the seed. Most seeds come from fruits, and the seeds are free of the fruit, unlike nuts such as hazelnuts, hickories, chestnuts and acorns, which have a stony fruit wall and originate from a compound ovary.