Which phrase is the best definition of sexual reproduction in plants

Fertilization.

Explanation:

Sexual reproduction involves two parent organisms. The parents here give rise to reproductive cells called gametes by a kind of cell division called meiosis. A gamete here contains a copy of part of the hereditary information organism which produced it.

During plant reproduction which is a diploid phase, also called sporophyte, it produces spores by meiosis that germinate and then divide by mitosis to form a haploid multicellular phase, the gametes here that produces gametes directly by mitosis. This form of life cycle, involving alternation between two multicellular phases.

During sexual reproduction, a gamete from one parent fusses with a gamete from another parent.