From where does the fern get the carbon dioxide required for photosynthesis?

From the air.

Explanation: On the surface of the leaves of the plants there are a large number of tiny pores known as stomata or stoma. For photosynthesis, green plants take carbon dioxide from the air. The carbon dioxide enters the leaves of the plant through the stomata present on their surface.

The summary of the circumstance would be listed below.

Explanation:

Fertilization would be a mechanism in which a father's sperm, as well as mom's egg, combine to produce a zygote. Since fertilizer application diploid (2n) combination of chromosomes or combinations between chromosome combinations throughout the zygote. Including both egg as well as sperm produce the cell recognized as haploid (n) quantities of homologous pairs via the meiosis mechanism at either the sperm production as well as oogenesis stages. Within a week of fertilization, this same zygote produces combinations of homologous genes borne mostly by parents.