Who deduced the double-helical structure of DNA?

The correct answer is Option (4) → James Watson and Francis Crick

NCERT (2026-27 edition):
Structure of Nucleic Acids – “… James Watson and Francis Crick gave a double strand helix structure for DNA (Fig. 10.7). Two nucleic acid chains are wound about each other and held together by hydrogen bonds between pairs of bases.”

Fig. 10.7: Double strand helix structure for DNA