An ulcer caused by H. pylori can be successfully treated with which classification of drugs?

The correct answer is D: Antibiotics. H. pylori is a bacterium that causes ulcers, so antibiotics are necessary to target and eliminate the bacteria. H2-receptor blockers (A) and proton-pump inhibitors (C) help reduce stomach acid but do not directly treat the infection. Antacids (B) only provide temporary relief by neutralizing stomach acid. Choice E, F, and G are not relevant options for treating H. pylori ulcers. In summary, antibiotics are essential to eradicate the bacterial infection and promote ulcer healing.