The rapidity and cost-efficiency of DNA sequencing has made it possible to sequence virtually all of the genes present in the microbes of a given habitat. This generates a collective genome for that habitat, which has come to be called a(n) .
metagenome

Metagenome.

Explanation:

Metagenomics is the study of genetic material recovered directly from environmental samples. The broad field may also be referred to as environmental genomics, ecogenomics or community genomics.

A metagenome is DNA from a group of species. In metagenomics, a metagenome is collected from an environmental sample and sequenced. Again, computer software accomplishes the task of

sorting out the partial sequences and assembling them into specific genomes. The ability to sequence

the DNA of mixed populations eliminates the need to culture each species separately

i think the answer is b.