**Core Concept**
The question is testing the pharmacological properties of expectorants, specifically their mechanism of action and side effects. Expectorants are medications that help loosen and thin mucus, making it easier to cough up. Gastric irritation and reflex increase in bronchial gland secretions are potential side effects of certain expectorants.

**Why the Correct Answer is Right**
The correct answer is likely ipecacuanha, which is an alkaloid derived from the roots of the ipecacuanha plant. Ipecacuanha works by stimulating the vagus nerve, leading to an increase in bronchial gland secretions and a reflex increase in respiratory rate. This stimulation can also cause gastric irritation due to the release of histamine and other mediators.

**Why Each Wrong Option is Incorrect**
* **Option A:** Guaifenesin is a common expectorant that works by increasing the fluidity of mucus, but it does not typically cause gastric irritation or reflex increase in bronchial gland secretions.
* **Option B:** Acetylcysteine is a mucolytic agent that breaks down mucus, but it does not have expectorant properties or cause gastric irritation.
* **Option D:** Ambroxol is an expectorant that works by stimulating the release of surfactant and increasing the fluidity of mucus, but it is not typically associated with gastric irritation.

**Clinical Pearl / High-Yield Fact**
Ipecacuanha was once used as a treatment for various conditions, including respiratory infections and diarrhea, but its use has declined due to the availability of safer alternatives. It is still used in some over-the-counter cough syrups and expectorants.

**Correct Answer: C. Ipecacuanha**