Answer: Option A. "tetracyclines"
Step-by-step explanation:
Tetracyclines are defined as a group of broad-spectrum antibiotics that are either isolated directly from several species of Streptomyces bacteria or can be synthesised semi-synthetically.
Tetracyclines act as inhibitors of growth rather than killing the infectious agent. Tetracyclines passively diffuse through porin channels present in bacterial membrane. it reversibly bind to the bacterial 30S ribosomal subunit to inhibit protein synthesis and prevents the aminoacyl transfer ribonucleic acid (tRNA) from binding to A site of the ribosome.
Hence, it is proved that tetracyclines bind to 30s ribosomal subunit rather than 50S ribosomal subunit in the ribososmes.