Out of the following radioactive substances which are not found in naturally on Earth?
Tritium
Deuterium
Uranium
Plutonium

Options

A. I and II
B. II and III
C. I and IV
D. I and III

Answer

To solve the question of which radioactive substances are not found naturally on Earth from the given options (Tritium, Deuterium, Uranium, Plutonium), we can follow these steps:

### Step 1: Understand the substances
- **Tritium (³H)**: A radioactive isotope of hydrogen. It has a half-life of about 12.3 years.
- **Deuterium (²H)**: A stable isotope of hydrogen. It is naturally found in small amounts in water.
- **Uranium (²³⁵U and ²³⁸U)**: Naturally occurring radioactive elements found in the Earth's crust.
- **Plutonium (²⁴¹Pu)**: A man-made radioactive element, primarily produced in nuclear reactors.

### Step 2: Analyze the half-lives
- Tritium has a relatively short half-life, which means it decays quickly. While it can be produced in small amounts in the atmosphere, its natural abundance is very low.
- Deuterium is stable and found naturally in water, so it is not considered in this context.
- Uranium is abundant in nature and is mined for nuclear fuel.
- Plutonium does not occur naturally in significant amounts; it is primarily produced in nuclear reactors from uranium.

### Step 3: Identify which substances are not found naturally
From the analysis:
- Tritium is present in trace amounts but is not found in significant quantities.
- Deuterium is naturally occurring.
- Uranium is naturally occurring.
- Plutonium is not found naturally and is man-made.

### Conclusion
The substances that are not found in significant natural quantities on Earth are Tritium and Plutonium.

Thus, the answer to the question is:
**Tritium and Plutonium.**