Q; a nucleotide consists of ?
a: a sugar, a protein and uracil
b: a phosphate, a sugar and a nitrogen base
c: a phosphate, an amino acid and a nitrogen base
d: a sugar and a nitrogen base

Option B, A phosphate, a sugar and a nitrogen base

Explanation:

Nucleotide is a basic building unit of DNA. Each nucleotide comprises of three major constituents – a) A sugar, b) A phosphate and c) a nitrogenous base.  

While forming a DNA molecule, deoxyribose acts as a specific sugar. When the nucleotides are linked together, they are supported by the phosphate bond and sugar as backbone. The two strands of DNA attaches to each other through the  nitrogenous bases in a way that nitrogenous base of one nucleotide attached to the nitrogenous base of other nucleotide through hydrogen bonds.  

Hence, option B is correct