Hint It is the male part of the angiosperms that produces sperm, they are flowering plants which are the most diverse group of and consist of the fruits which contain seed. The flower helps with the fertilization of the ovule and development of fruit which consists of seed.
The male gametophyte of angiosperm is Pollen after germination. Megagametophyte is the egg which produces gametophyte and the sperm which produces gametophyte is known as the microgametophyte. In seed plants, the microgametophyte is known as Pollen and it consists of two or more cells when the pollen grains exit from the sporangium. In the megasporangium, the megagametophyte develops and to an extent seedless vascular plants are produced in a cone or flower in seed plants. The pollen grain or the microgametophyte travels to the vicinity of the egg cell in seed plants which is carried by animal vector or physical vector and produces two sperms by the process of mitosis. The pollen grains get developed in the stamen which comprises filament supporting the anther and the vascular bundles present in the filament helps in the conduction of nutrients from the mother plant to the anther.
The mature male gametophyte of flowering plants is simple during its developmental stage and goes under a series of differentiation events. For the development, a large number of genes are required which are expressed during Pollen development and appear to express in the sporophyte also. Send the Pollen specific genes are expressed to promoter elements for the requirement of male gametophyte specific gene regulation. In the mature Pollen, the mRNAs are identified as the metabolic genes which are involved in the Pollen tube growth in the style. The function of pollen-specific genes have been isolated and the occurrence during Pollen tube growth is the primary synthetic event which is concerned with the Pollen tube wall synthesis and the synthesis of the cell membrane. To identify many gene products it is difficult in the pollen grain which is involved with the tube wall synthesis.
So, the correct answer is 'Pollen after germination'.
Note: Angiosperms appeared around 140 million years ago and are the first species to be known in the plant Kingdom some angiosperms species of flowers are used as a source of food which consists of broccoli which is considered a vegetable and saffron which is a type of crocus flower.