Which of the following statement is incorrect :

Options

A. `O_2` is paramagnetic , `O_3` is also paramagnetic
B. `O_2` is paramagnetic , `O_3` is diamagnetic
C. `B_2` is paramagnetic , `C_2` is also paramagnetic
D. Different observation is found in their bond length when NO `to NO^(+)` and `COtoCO^+`

Explanation

To determine which of the statements is incorrect, we will analyze each option provided in the question regarding the magnetic properties and bond lengths of the given molecules.

### Step-by-step Solution:

1. **Analyzing O2:**
- O2 (dioxygen) has a molecular orbital configuration that results in two unpaired electrons in its anti-bonding π* orbitals.
- Since it has unpaired electrons, O2 is **paramagnetic**.

2. **Analyzing O3:**
- O3 (ozone) has a different molecular structure and bonding. It has no unpaired electrons in its molecular orbital configuration.
- Therefore, O3 is **diamagnetic**.

3. **Analyzing B2:**
- B2 (diboron) has a molecular orbital configuration that results in two unpaired electrons.
- Thus, B2 is also **paramagnetic**.

4. **Analyzing C2:**
- C2 (dicarbon) has a molecular orbital configuration that results in all electrons being paired.
- Therefore, C2 is **diamagnetic**.

5. **Analyzing NO and CO:**
- When considering the ions NO+ and CO+, both species have a decrease in bond length compared to their neutral counterparts (NO and CO).
- This is because the removal of an electron typically leads to stronger bonding interactions, thus decreasing bond length.

6. **Identifying Incorrect Statements:**
- From the analysis:
- Statement about O2 being paramagnetic is correct.
- Statement about O3 being paramagnetic is **incorrect** (it is diamagnetic).
- Statement about B2 being paramagnetic is correct.
- Statement about C2 being diamagnetic is correct.
- Statement about bond lengths in NO and CO is correct.

### Conclusion:
The incorrect statement is regarding O3 being paramagnetic. Therefore, the answer is **A** (O3 is paramagnetic).