Gymnosperms do not bear fruits because they do not have

The correct option is B Ovary
Gymnosperms, example. Cycas, Pinus, Cedrus etc, bear reproductive structures in the form of cones. The cones that bear female reproductive structures are called female cones. Each female cone contains spirally arranged megasporophylls, that have ovules directly attached to them, that is,ovules not enclosed in the ovary or are naked. After fertilization the ovule forms the seed and the ovary forms the fruit. Since, in gymnosperms ovary is absent fruits are not formed.

So, the correct answer is 'Ovary'