**Core Concept**
Tetracyclines are a class of broad-spectrum antibiotics that exert their antibacterial effects by inhibiting protein synthesis in bacteria. This is achieved through the binding of the antibiotic to the bacterial ribosome, which is essential for the translation of messenger RNA (mRNA) into a polypeptide chain.

**Why the Correct Answer is Right**
Tetracyclines bind to the 30S subunit of the bacterial ribosome, specifically to the 16S rRNA, and prevent the attachment of aminoacyl-tRNA to the ribosomal acceptor site. This prevents the addition of new amino acids to the growing polypeptide chain, thereby inhibiting protein synthesis. The binding of tetracyclines to the ribosome is non-covalent and reversible, and the antibiotic can be removed from the ribosome once the bacterial cell is exposed to a sufficient concentration of tetracycline.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely to be incorrect, but the actual option is not provided.
**Option B:** This option is incorrect because tetracyclines do not act by inhibiting the initiation of protein synthesis, but rather by preventing the elongation of the polypeptide chain.
**Option C:** This option is incorrect because tetracyclines do not act by inhibiting the synthesis of DNA, but rather by inhibiting protein synthesis.

**Clinical Pearl / High-Yield Fact**
Tetracyclines are contraindicated in pregnancy due to the risk of inhibiting bone growth and causing tooth discoloration in the developing fetus. Additionally, tetracyclines can cause photosensitivity reactions in some individuals, and patients should be advised to avoid sun exposure while taking these antibiotics.

**Correct Answer: C. 30S ribosomal subunit**