Explanation:

• Scientists from the CSIR-Institute of Genomics and Integrative Biology, New Delhi, have developed an enhanced genome-editing system that can modify DNA more precisely and more efficiently than existing CRISPR-based technologies.

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR-Cas9)

• It is a Gene Editing tool and is a precise way of altering DNA. It cuts out specific strands of DNA, and replaces them with new strands.

• CRISPR: It is the DNA-targeting part of the system which consists of an RNA molecule, or ‘guide’, designed to bind to specific DNA bases through complementary base-pairing.

• Cas9: It stands for CRISPR-associated protein 9, & is the nuclease part that cuts the DNA.

• The CRISPR-Cas9 system: The technology was adapted from a naturally occurring genome editing system used by bacteria as an immune defense. 

• It helps the organisms recognise and fight off similar viruses in the future by acting  like an immune system. 

 Hence option 4th is correct.