Answer:
The correct order of size - base pair < gene < chromosome.
Step-by-step explanation:
Nitrogen base-pair attaches with the phosphate group and a sugar molecule to form a building block of DNA or nucleic acids. Nucleic acids make the gene is the physical and functional unit of hereditary that takes the information from parent cells to daughter cells.
Chromosomes are a structure that appears thread-like and makes the genome with different chromosomes. These structures are made up of wrapped DNA or genes around histone proteins.