The length of $Mycobacterium$ $tuberculosis$ is: (in $\mu m$)

In the vast marine ecosystem, certain seas develop red colouration. This red colour is due to the presence of a large population of which one of the following organisms?

Which of the following may be used in the reclamation of soil?

Which of the following statements is correct for both blue-green algae and bacteria?

Cell wall is absent in

Which one of the following is a prokaryote?