Halophilic archaebacterium (Halobacterium salinarum) found in the Great Salt Lake and the Dead Sea cannot live in
(A) Less than $3M$$NaCl$concentration
(B) Less than \[5M\]$NaCl$concentration
(C) More than $4M$$NaCl$concentration
(D) More than $3M$$NaCl$concentration

Hint:Halophilic archaebacterium (Halobacterium salinarum) are the examples of halophiles.The halophiles are the type of microorganisms which are mostly proper and grow in an environment having greater salt concentration.So, it has been observed that these organisms cannot thrive in an environment having a concentration less than $3M$.

Complete answer:
Halophiles are also known as salt-loving organisms.These microorganisms are abundantly found in the environments having high salinity such as deep-sea, arid, salt mines, coastal areas and others.They can continually exist in evaporating ponds and salt lakes including Great Salt Lake, Dead Sea and others.They cannot survive in an environment or habitat that has concentration less than $3M$$NaCl$.Moreover, if the concentration of $NaCl$ in the environment gets more than $3M$, it can significantly lead to the movement of water from outside of a plant cell towards the environment and this can cause death of the cell due to osmotic pressure.Therefore it is very necessary to maintain the salt ($NaCl$) concentration within $3M$ so as to keep the Halobacterium salinarum, mostly originating in the Great Salt Lake and the Dead Sea.

Hence the correct answer is option ‘A’.

Note: One of the most known mechanisms associated with the survival of the Halophiles bacteria and Archaea in extreme concentrations of salt is that they potentially synthesize the osmoprotectants, also recognized as compatible solutes.These assist the halophile to balance and maintain the internal osmotic pressure as compared to the external osmotic pressure, allowing the two solutions to behave as isotonic.