**Core Concept**
Induction agents are a class of anesthetic medications used to initiate general anesthesia. They work by depressing the central nervous system, which can lead to respiratory depression, a potentially life-threatening complication. The degree of respiratory depression varies among different induction agents, and some are safer than others in this regard.

**Why the Correct Answer is Right**
The correct answer is **C. Propofol**. Propofol is a short-acting induction agent that has a minimal impact on respiratory function. It is a GABA receptor agonist, which enhances the effect of the inhibitory neurotransmitter GABA, leading to sedation and hypnosis. Propofol's rapid onset and short duration of action make it an ideal choice for induction, and its minimal respiratory depressant effects make it a safer option in this regard.

**Why Each Wrong Option is Incorrect**
**Option A:** Thiopentone is a barbiturate induction agent that causes significant respiratory depression due to its ability to depress the respiratory centers in the brainstem. It also has a slower onset of action compared to propofol.
**Option B:** Etomidate is another induction agent that can cause respiratory depression, although to a lesser extent than thiopentone. However, it is not as safe as propofol in this regard.
**Option D:** Ketamine is a dissociative anesthetic that can cause significant respiratory depression, especially at higher doses. It also has a slower onset of action compared to propofol.

**Clinical Pearl / High-Yield Fact**
Propofol is a good choice for induction in patients with respiratory disease, as it has a minimal impact on respiratory function. However, it should be used with caution in patients with liver disease, as it can cause propofol infusion syndrome, a potentially life-threatening condition.

**Correct Answer:** C. Propofol