Fill in the blanks:

(a) Microorganisms can be seen with the help of a ________.


(b) Blue green algae fix _______directly from air to enhance fertility of soil.


(c) Alcohol is produced with the help of _______.


(d) Cholera is caused by_______.

(a) Microscope

(b) Nitrogen


(c) Yeast


(d) Bacteria


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