Presence of which reagent will affect the reversibility of the following reaction, and change it to a irreversible reaction :

CH₄ + I₂ $$\mathrel{\mathop{\kern0pt\rightleftharpoons} \limits_{{\mathop{\rm Re}\nolimits} versible}^{hv}} $$ CH₃ $$-$$ I + HI

Which one among the following chemical tests is used to distinguish monosaccharide from disaccharide?

Consider the above reaction and identify the Product P :

The compound 'A' is a complementary base of _______________ in DNA stands.