Which of the following statements are correct?

Options

A. A reaction in which different stereoisomers produced different products or act a different rates is called stereospecific reaction.
B. A reaction in which a given substrate produces diastereoisomeric products in different amounts and where one diastereomer predominates very much over the other is called stereoselective reaction.
C. If the replacement of one group at an achiral centre by a new substituent generates a chiral centre by a new substituent generates a chiral centre, the original molecule is said to be enantiotopic.
D. The `E` and `Z` system of naming geometrical isomers is based on the `CIP` sequence rule.

Explanation

To determine which of the statements provided are correct, we will analyze each statement one by one based on the principles of isomerism in chemistry.

### Step-by-Step Solution:

1. **Statement 1**: "A reaction in which different stereoisomers produce different products or act at different rates is called a stereospecific reaction."
- **Analysis**: This statement defines a stereospecific reaction accurately. In stereospecific reactions, the stereochemistry of the reactants influences the stereochemistry of the products, leading to different products or rates based on the stereoisomer involved.
- **Conclusion**: This statement is **correct**.

2. **Statement 2**: "A reaction in which a given substrate produces diastereoisomeric products in different amounts, where one diastereomer predominates over the other, is called a stereoselective reaction."
- **Analysis**: This statement correctly describes a stereoselective reaction. In such reactions, one diastereomer is favored over another, leading to an unequal distribution of products.
- **Conclusion**: This statement is **correct**.

3. **Statement 3**: "If the replacement of one group at a chiral center by a new substituent generates a new chiral center, the original molecule is said to be enantiotropic."
- **Analysis**: The term "enantiotropic" is used to describe systems that can interconvert between enantiomers. The statement correctly indicates that the replacement of a group at a chiral center can lead to the formation of a new chiral center, which supports the definition of enantiotropic behavior.
- **Conclusion**: This statement is **correct**.

4. **Statement 4**: "The E and Z system of naming geometrical isomers is based on the CIP sequence rule."
- **Analysis**: The E/Z nomenclature indeed relies on the Cahn-Ingold-Prelog (CIP) priority rules to assign priorities to substituents around a double bond. This system helps in distinguishing between geometrical isomers based on the arrangement of these substituents.
- **Conclusion**: This statement is **correct**.

### Final Conclusion:
All four statements are correct.