Question

A) Chromosome
B) DNA nucleotide
C) Codon
D) Gene
Place the components in order, from smallest to largest.
A) A0B0D0C
B) B0C0D0A
C) C0D0B0A
D) D0C0B0A

Answer 1

since gene has multiple codons 
and codon has 3 sequence of nucleotides, 

The smallest would be a DNA nucleotide , then a codon, then a gene and finally a chromosome!

so the answer is B