When these two gametes (an egg and a sperm) combine with each other, the process is known as fertilization (as we can see in the third answer option), and this is achieved by these two sexual cells by a set of physiological reactions in which both cells are involved, for example, they can chemically attract between each other. After this process, also known as fecundation, there would be the formation of a zygote, which will end in the formation of an embryo after embryogenesis. We can see this graphically in the picture below, where there're a sperm and an egg with their parts.