A nucleoside on hydrolysis gives

an aldopentose and a heterocyclic base

The correct answer is option 1. an aldopentose and a heterocyclic base.

A nucleoside is a molecule consisting of two components:

(i) A pentose sugar (either ribose or deoxyribose, both classified as aldoses)

(ii) A nitrogenous base (either a purine or a pyrimidine)

Hydrolysis is a process that breaks down a molecule using water.

In the case of a nucleoside, hydrolysis cleaves the bond between the sugar and the nitrogenous base, resulting in:

(i) An aldopentose sugar (ribose or deoxyribose)

(ii) A heterocyclic base (purine or pyrimidine)

Option 2 and 3 are incorrect because nucleosides don't contain a phosphate group.

Option 4 is incorrect because while hydrolysis yields the two components, it doesn't break down the sugar further.