Which statement is/are correct
(a) Formation of anions with unit charge (e.g`CI^(Θ) Br^(Θ),Br^(Θ),I^(Θ)` are very common because the `EA` of these atoms is positive and quite high or `Delta_(eg)H^(Θ)` of these atoms are negative and quite high
(b) `EA'` or `Delta_(eg)H^(Θ)` of these atoms is positive and quite high
(c ) Formation of anions with -23 charge `(e.g.S^(2-),O^(2))` is not so easy as their second `EA"` are negative i.e energy is needed to add second electron
(d) Formation of anions with `-3` charge `(e.g. N^(3-),p^(3-))` is almost rare as the third `Delta_(eg)H^(Θ)` are positive i,e energy in needed to add third electron .

Explanation

To determine which statements regarding the formation of anions are correct, we will analyze each statement one by one based on the concepts of electron affinity (EA) and electron gain enthalpy (ΔegH).

### Step-by-Step Solution:

1. **Understanding Electron Affinity and Electron Gain Enthalpy:**
- Electron affinity (EA) is the energy change when an electron is added to a neutral atom in the gas phase. It is usually expressed as a positive value, indicating energy is released.
- Electron gain enthalpy (ΔegH) is the energy change associated with the addition of an electron to an isolated gaseous atom. For the first electron, this value is negative, indicating that energy is released when an electron is added.

2. **Analyzing Statement (a):**
- The statement claims that the formation of anions with a unit charge (e.g., Cl⁻, Br⁻, I⁻) is common because the EA of these atoms is positive and quite high, and the ΔegH is negative and quite high.
- **Evaluation:** This statement is correct. The halogens have high electron affinities, which means they readily accept an electron, and their ΔegH is negative, indicating that energy is released during this process.

3. **Analyzing Statement (b):**
- This statement claims that both EA and ΔegH of these atoms are positive and quite high.
- **Evaluation:** This statement is incorrect. While EA is positive, ΔegH for the first electron is negative. Therefore, this statement is false.

4. **Analyzing Statement (c):**
- This statement discusses the formation of anions with a -2 charge (e.g., S²⁻, O²⁻) and states that it is not easy because their second EA is negative, meaning energy is required to add a second electron.
- **Evaluation:** This statement is correct. The addition of a second electron to an already negatively charged ion involves repulsion between the two negative charges, making it energetically unfavorable.

5. **Analyzing Statement (d):**
- This statement refers to the formation of anions with a -3 charge (e.g., N³⁻, P³⁻) and states that this is rare because the third ΔegH is positive, indicating energy is needed to add a third electron.
- **Evaluation:** This statement is also correct. The addition of a third electron faces significant electrostatic repulsion, making the process energetically unfavorable.

### Conclusion:
Based on the analysis:
- Statement (a) is **correct**.
- Statement (b) is **incorrect**.
- Statement (c) is **correct**.
- Statement (d) is **correct**.

Thus, the correct statements are (a), (c), and (d).