Why Is There a New Reliance on Metagenomics to Find

Why is there a new reliance on metagenomics to find new organisms that may produce a medically or industrially important product?

A) So far,only about 10% of useful microbes have been grown in the laboratory.
B) Soils contain so many potential sources of microbes producing antibiotics it would take more than a century to screen them all.
C) We do not have the techniques for growing most microbes found in nature.
D) All of these argue for the need to use metagenomics to identify new useful microbial products.