Which of the following acts as rocket propellants?

Options

A. Liq.`H_(2)`+Liq.`O_(2)`
B. Liq.`N_(2)`+Liq.`O_(2)`
C. Liq.`H_(2)`+Liq.`N_(2)`
D. Liq.`O_(2)`+Liq. Argon

Answer

To determine which of the given options acts as rocket propellants, we need to analyze each option based on the principles of rocket propulsion.

### Step-by-Step Solution:

1. **Understanding Rocket Propellants**: Rocket propellants are substances that are used in rocket engines to produce thrust. They typically consist of a fuel and an oxidizer that undergo a chemical reaction to produce hot gases.

2. **Analyzing the Options**:
- **Option A: Liquid Hydrogen + Liquid Oxygen**: This combination is well-known in rocket propulsion. Liquid hydrogen serves as the fuel, while liquid oxygen acts as the oxidizer. When they react, they produce water vapor and a significant amount of energy, generating thrust.

- **Option B: Liquid Nitrogen + Liquid Oxygen**: Liquid nitrogen is not a fuel; it is an inert gas under normal conditions and does not combust with liquid oxygen. Therefore, this combination is not effective as a rocket propellant.

- **Option C: Liquid Hydrogen + Liquid Nitrogen**: Similar to option B, liquid nitrogen does not act as an oxidizer and cannot support combustion with liquid hydrogen. Hence, this combination is also not a suitable rocket propellant.

- **Option D: Liquid Oxygen + Liquid Argon**: Liquid argon is an inert gas and does not react with liquid oxygen to produce thrust. Thus, this combination is not effective as a rocket propellant.

3. **Conclusion**: After analyzing all the options, the only viable combination that acts as a rocket propellant is **Liquid Hydrogen + Liquid Oxygen**.

### Final Answer:
The correct option is **Liquid Hydrogen + Liquid Oxygen**.

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