Archaebacteria differ from eubacteria in (А) Cell membrane structure (B) Mode of nutrition (С) Cell shape (D) Mode of reproduction

Archaebacteria (also known as Archaea) and eubacteria (also known as Bacteria) are two distinct domains of single-celled microorganisms. They differ in several ways, including cell membrane structure, mode of nutrition, cell shape, and mode of reproduction. Specifically:

(A) Cell membrane structure: Archaebacteria have unique cell membrane structures that are fundamentally different from those of eubacteria. The cell membranes of archaebacteria often contain branched hydrocarbon chains in their lipid bilayers, whereas eubacteria typically have straight-chain fatty acids in their lipid bilayers.

(B) Mode of nutrition: Both archaebacteria and eubacteria can exhibit a range of nutritional modes, including autotrophy (producing their own food through photosynthesis or chemosynthesis) and heterotrophy (obtaining food by consuming other organic matter). There isn't a significant difference in this aspect between the two groups.

(C) Cell shape: Both archaebacteria and eubacteria can exhibit various cell shapes, such as cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-shaped). There isn't a consistent difference in cell shape between the two groups.

(D) Mode of reproduction: Both archaebacteria and eubacteria reproduce asexually through processes such as binary fission, budding, or fragmentation. Again, there isn't a significant difference in this aspect between the two groups.

Given the options provided, none of them accurately capture the main distinguishing features between archaebacteria and eubacteria. However, if forced to choose from the options, (А) Cell membrane structure would be the closest to representing a key difference between the two groups.