Final answer:
In mosses, A) antheridia are the structures that produce sperm. They produce many flagellated sperm that are capable of travelling to the female structures, archegonia, which produce eggs.
Step-by-step explanation:
In mosses, the structures that produce sperm are called antheridia, which are the male reproductive organs. These antheridia generate many mobile sperm with flagella, enabling them to travel towards the female reproductive structures called archegonia to achieve fertilization. The archegonia, on the other hand, each produce a single immobile egg within their flask-shaped form. The gametophytes in mosses produce these reproductive structures, and it's important to note that the process of gamete production in these organisms does not involve meiosis, as the gametophyte cells are already haploid. Instead, cells divide in a pattern that leads to the formation of antheridia and archegonia.