The correct option is 4: The core concept tested here revolves around the fundamental classification of life into prokaryotes and eukaryotes. The defining characteristic of a eukaryotic cell is the presence of internal membrane-bound organelles, most importantly the nucleus, which is enclosed by a nuclear membrane. In contrast, prokaryotic cells, which include bacteria and archaea, completely lack a true nucleus and other membrane-bound organelles. Nostoc is a filamentous cyanobacterium, and…Read More