Archaebacteria differs from eubacteria in
A. Mode of nutrition
B. Cell shape
C. Mode of reproduction
D. Cell membrane structure

Hint: Both these Archaebacteria and Eubacteria are single celled prokaryotic microorganisms. Archaebacteria are found in extreme environmental conditions and eubacteria are found everywhere. These are known to be the oldest found organisms on the earth.

Complete answer:
Archaebacteria usually have the same shape and size as other bacteria. Nutrition and appearance of archaebacteria is also like other bacteria. These reproduce by binary fission. Due to their existence in extreme environmental conditions archaebacteria has a different cell membrane structure that helps them in surviving in such conditions.

> Option A - Mode of nutrition in archaebacteria is the same as other bacteria. They are said to have an autotrophic mode of nutrition.

> Option B - The size and shape of Archaebacteria is the same as that of eubacteria so there is no such difference present on the basis of cell shape in archaebacteria.

> Option C - This is also a similar characteristic of archaebacteria with the eubacteria. They reproduce from binary fission mode of reproduction.

> Option D - The cell membrane in archaebacteria is made of glycerol-ether lipid and in eubacteria it is made up of glycerol-ester lipid. Ether lipids present in the cell membrane of archaebacteria are more resistant this is why they survive in harsh conditions.

Hence, the correct answer is option (D).

Note: Archaebacteria are the oldest living organisms on the earth known so far. They resemble bacteria and belong to the kingdom monera. After all this they are very different from prokaryotes but have common features with eukaryotes.