Correct Option
Assertion (A) states that Amoeba reproduces by fission. Amoeba is a unicellular eukaryotic organism. Its primary mode of reproduction is asexual, specifically binary fission, where the parent cell divides into two genetically identical daughter cells. Therefore, Assertion (A) is true.
Reason (R) states that all unicellular organisms reproduce by asexual methods. While some unicellular organisms (e.g., certain algae, fungi, or protozoa like Paramecium) can exhibit sexual processes or reproduction, the predominant and characteristic mode of reproduction for the vast majority of unicellular organisms, including bacteria and Amoeba, is asexual (e.g., binary fission, budding, multiple fission). In the context of general biological principles, this statement is considered largely true, emphasizing the prevalence of asexual reproduction in unicellular life forms. Therefore, Reason (R) is true.
Reason (R) provides a direct explanation for Assertion (A). Amoeba, being a unicellular organism, reproduces by fission because unicellular organisms characteristically reproduce through asexual methods like fission. Thus, R correctly explains A.
Incorrect Options
Options (2), (3), and (4) are incorrect because both Assertion (A) and Reason (R) are individually true, and Reason (R) serves as the correct explanation for Assertion (A). Option (2) incorrectly states that R is not the correct explanation. Options (3) and (4) are incorrect as they claim one of the statements (A or R) is false, which is not the case.