ETS is inhibited at complex -III by :

Options

A. Cyanide
B. Rotenone
C. Antimycin
D. Oligomycin

Answer

To solve the question "ETS is inhibited at complex -III by:", we need to analyze the options provided and understand the role of each inhibitor in the electron transport system (ETS).

### Step-by-Step Solution:

1. **Understand the Electron Transport System (ETS)**:
- The ETS is a series of protein complexes located in the inner mitochondrial membrane that facilitate the transfer of electrons derived from NADH and FADH2 to oxygen, ultimately producing ATP.

2. **Identify the Complexes**:
- The ETS consists of several complexes (Complex I, II, III, and IV) and ATP synthase. Each complex has a specific role in the electron transport process.

3. **Review the Options**:
- The options given are:
- A) Cyanide
- B) Rotenone
- C) Antimycin
- D) Oligomycin

4. **Determine the Inhibitors**:
- **Cyanide**: Inhibits Complex IV (cytochrome c oxidase).
- **Rotenone**: Inhibits Complex I (NADH dehydrogenase).
- **Antimycin**: Inhibits Complex III (cytochrome b-c1 complex).
- **Oligomycin**: Inhibits ATP synthase.

5. **Identify the Correct Answer**:
- Since the question specifically asks for the inhibitor of Complex III, the correct answer is **Antimycin**.

### Final Answer:
The correct answer is **C) Antimycin**.