Which describes orbital :-

Options

A. `Psi`
B. `Psi ^(2)`
C. `|Psi^(2)|Psi`
D. All

Explanation

To solve the question "Which describes orbital?", we need to analyze the given options and determine which one correctly describes an orbital in the context of atomic structure.

### Step-by-Step Solution:

1. **Understanding the term "orbital":**
An orbital is a mathematical function that describes the wave-like behavior of electrons in an atom. It is characterized by a wave function, which provides information about the probability of finding an electron in a particular region around the nucleus.

2. **Analyzing Option A: psi (Ψ):**
- The symbol psi (Ψ) represents the wave function of an electron in quantum mechanics.
- It describes the amplitude of the orbital and is fundamental to understanding the behavior of electrons in atoms.
- **Conclusion:** This option describes an orbital.

3. **Analyzing Option B: psi squared (Ψ²):**
- Psi squared (Ψ²) represents the probability density of finding an electron in a particular region of space.
- While it is related to orbitals, it does not describe the orbital itself; rather, it describes the probability associated with the orbital.
- **Conclusion:** This option does not describe an orbital.

4. **Analyzing Option C: psi squared times psi (Ψ²Ψ):**
- This expression combines the probability density with the wave function, but it does not provide a clear description of an orbital.
- It is not a standard term used to describe orbitals in quantum mechanics.
- **Conclusion:** This option does not describe an orbital.

5. **Analyzing Option D: (not specified, but assumed incorrect based on previous analysis):**
- Since options B and C have already been determined to be incorrect, and option A is the only one that describes an orbital, we conclude that option D is also incorrect.

### Final Conclusion:
The correct option that describes an orbital is **Option A: psi (Ψ)**.