| Primary Sewage treatment | Secondary sewage treatment | |
| It is a mechanical process involving the removal of coarse solid materials. | 1 | It is a biological process involving the action of microbes. |
| It is inexpensive and relatively less complicated. | 2 | It is a very expensive and complicated process. |


Observe the given sequence of nitrogenous bases on a DNA fragment and answer the following questions: 
(a) Name the restriction enzyme which can recognise the DNA sequence.
(b) Write the sequence after restriction enzyme cut the palindrome.
(c) Why are the ends generated after digestion called as ‘Sticky Ends’?

There are several valuable microorganisms that are beneficial to humans in various manners such as: