Correct option (a) gene library
Explanation :
Gene library is a collection of cloned DNA fragments representing the entire genetic material of an organism. The aggregate of all the genes and their alleles present in an interbreeding population is known as gene pool. Genome is a complete set of chromosomes where every gene/chromosome is represented singly as in a gamete. In bacteria the heredity material is mainly made of spherical or cylindrical structure called nucleoid (genophore).