DNA strands are anti-parallel because of:

Correct Answer: (A) Hydrogen bonds

Explanation:

• Hydrogen bonds: Hold the complementary nitrogenous bases together (A-T forms two bonds, G-C forms three bonds) in an anti-parallel orientation.
• Phosphodiester bonds: Link the 5' phosphate of one nucleotide to the 3' hydroxyl of the next nucleotide, forming the sugar-phosphate backbone.
• Disulphide bonds: These occur in proteins, not DNA.
• Glycosidic bonds: Link the sugar and nitrogenous base in nucleotides.