The answer of your question is : Option 3-Below the gravity.

Explanation:
The centre of pressureis the point where the total sum of apressure field acts on a body.When a body is immersed in a fluid,it experiences a pressure and this pressure increases with the depth.As pressure is higher at deeper levels  the lower body experiences  more pressure as compared to upper body. Therefore, the centre of pressure in immersed body is below gravity.

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