The cells of the bacterium $Streptococcus$ remain arranged in the form of

Which of the following is considered the most primitive?

Organisms that obtain energy by the oxidation of reduced inorganic compounds are called .............

Which among the following are the smallest living cells,known without a definite cell wall,pathogenic to plants as well as animals and can survive without oxygen?

Which of the following statements are incorrect for $Nostoc$ and $Anabaena$?
$(a)$. Possess tissue level organization
$(b)$. Have heterocysts
$(c)$. Can fix atmospheric hydrogen
$(d)$. They are eubacteria

The highly resistant nature of an endospore is due to the presence of: