What type of sugar forms the backbone of RNA?

The correct answer is Option (3) → Ribose sugar

A nucleotide has three parts: a nitrogenous base, a pentose (five-carbon) sugar and a phosphate group. The sugar and phosphate groups join to form the backbone of the chain. In RNA the sugar is ribose; in DNA it is deoxyribose. The ribose of RNA carries an extra –OH group at the 2′ position. Glucose and other hexoses have six carbons and are not part of nucleic acids.

NCERT Extract:
Structure of Polynucleotide Chain – “… A nucleotide has three components – a nitrogenous base, a pentose sugar (ribose in case of RNA, and deoxyribose for DNA), and a phosphate group. … In RNA, every nucleotide residue has an additional –OH group present at 2′ -position in the ribose.”