Which of the following is used as rocket fuel?

Options

A. Liquid `O_(2)`
B. liquid `NH_(3)`
C. Liquid `N_(2)`
D. Liquid `H_(2)`

Answer

To determine which of the given options is used as rocket fuel, let's analyze each option step by step.

### Step 1: Identify the options
The options provided are:
1. Liquid Oxygen (LOX)
2. Liquid Ammonia (NH3)
3. Liquid Nitrogen (LN2)
4. Liquid Hydrogen (LH2)

### Step 2: Understand the role of each substance
- **Liquid Oxygen (LOX)**: Often used as an oxidizer in rocket fuel combinations but not a fuel by itself.
- **Liquid Ammonia (NH3)**: Can be used as a fuel in some rocket designs, but it is not commonly used in major space missions.
- **Liquid Nitrogen (LN2)**: Primarily used for cooling and not as a fuel.
- **Liquid Hydrogen (LH2)**: Widely recognized as a primary fuel for many rockets due to its high efficiency and energy output.

### Step 3: Determine the most suitable option
Among the options, **Liquid Hydrogen (LH2)** is the most commonly used rocket fuel. It is utilized in many space missions, including the Space Shuttle and various other launch vehicles.

### Conclusion
The correct answer is **Liquid Hydrogen (LH2)**, which is option D.

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