Binary fission is the method of asexual reproduction in unicellular organisms. It is the process in which the parent divides into two daughter cells that are genetically and morphologically similar. During this process, the nucleus divides into two, followed by the division of the cytoplasm.
Types of binary fission seen in the organisms are as follows: Simple binary fission, Transverse binary fission, and Longitudinal binary fission.
1. Simple binary fission: This type of binary fission occurs in irregular-shaped organisms such as Amoeba, in which the plane of division is difficult to ascertain.
2. Transverse binary fission: it is the method of the division at a right angle to the long axis of the animal e.g., Paramecium and Planaria.
3. Longitudinal binary fission: In this method division is parallel to the long axis, as in Euglena, Vorticella and in some corals.
Thus, the correct answer is option D.