A radioactive substance emits radiations :

Options

A. `alpha`, `beta` and `gamma` simultaneously
B. in the order `alpha`, `beta` and `gamma` one by one
C. X-rays and `gamma`-rays
D. `alpha` or `beta`.

Answer

To solve the question regarding the emissions from a radioactive substance, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Radioactive Emissions**:
- Radioactive substances can emit different types of radiation, namely alpha particles, beta particles, and gamma rays.

2. **Identifying Emission Types**:
- Alpha decay involves the emission of alpha particles (helium nuclei).
- Beta decay involves the emission of beta particles (electrons or positrons).
- Gamma decay involves the emission of gamma rays (high-energy photons).

3. **Analyzing Simultaneous Emissions**:
- It is important to note that in a single radioactive decay event, a substance cannot emit both alpha and beta particles simultaneously. They can emit one type at a time.

4. **Evaluating the Options**:
- **Option 1**: Alpha, beta, and gamma simultaneously - This is incorrect as alpha and beta cannot be emitted at the same time.
- **Option 2**: Alpha, beta, and gamma in order - This is also incorrect because it suggests that they can be emitted one after the other in a single decay event, which is not the case.
- **Option 3**: X-rays will not be emitted - This option is irrelevant as it does not pertain to the types of emissions discussed.
- **Option 4**: Alpha or beta - This is correct because a radioactive substance can emit either alpha or beta particles, and this can be accompanied by gamma emission.

5. **Conclusion**:
- The correct answer is that a radioactive substance emits either alpha or beta particles, possibly accompanied by gamma radiation.

### Final Answer:
The radioactive substance emits either alpha or beta particles.