Pickout the correct statements:

Options

A. Negative `beta`-decay decreases the proportion of neutrons and increases the proportion of proton
B. Positive `beta`-decay increases the proportion of neutrons and decreases the proportion of proton
C. `K`-electron capture increases the proportion of neutrons and increases the proportion of proton.
D. Positrons and electrons quickly unite to produce photons.

Answer

To solve the question of identifying the correct statements regarding nuclear decay processes, we will analyze each statement based on our understanding of beta decay, positron emission, and electron capture.

### Step-by-Step Solution:

1. **Understanding Negative Beta Decay**:
- In negative beta decay, a neutron in the nucleus is converted into a proton, emitting an electron (beta particle) and an antineutrino.
- This process decreases the number of neutrons and increases the number of protons in the nucleus.

**Statement A**: "Negative beta decay decreases the proportion of neutrons and increases the proportion of protons."
- This statement is **correct**.

2. **Understanding Positive Beta Decay**:
- Positive beta decay (or beta plus decay) involves the conversion of a proton into a neutron, emitting a positron and a neutrino.
- This process decreases the number of protons and increases the number of neutrons.

**Statement B**: "Positive beta decay increases the proportion of neutrons and decreases the proportion of protons."
- This statement is **correct**.

3. **Understanding K Electron Capture**:
- In K electron capture, an electron from the innermost shell is captured by the nucleus, where it combines with a proton to form a neutron and a neutrino.
- This process increases the proportion of neutrons and decreases the proportion of protons.

**Statement C**: "K electron capture increases the proportion of neutrons and increases the proportion of protons."
- This statement is **incorrect**. It should state that it increases the proportion of neutrons and decreases the proportion of protons.

4. **Understanding Positron Emission**:
- In positron emission, a proton is converted into a neutron, emitting a positron.
- This process also decreases the number of protons and increases the number of neutrons.

**Statement D**: "The positrons and electrons quickly unite to produce photons."
- This statement is **correct**. When a positron encounters an electron, they annihilate each other, producing gamma-ray photons.

### Conclusion:
Based on the analysis:
- **Correct Statements**: A, B, and D.
- **Incorrect Statement**: C.

### Final Answer:
The correct statements are A, B, and D.

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