Assertion : Geometrical isomerism is also called cis-trans isomerism .
Reason : Tetrahedral complexes show geometrical isomerism .

Options

A. If both Assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false
D. if both assertion and reason are false

Explanation

To solve the question regarding the assertion and reason provided, we will analyze both statements step by step.

### Step 1: Analyze the Assertion
- **Assertion**: "Geometrical isomerism is also called cis-trans isomerism."
- **Explanation**: This statement is correct. Geometrical isomerism refers to the different spatial arrangements of ligands around a central metal atom in a coordination compound. In the case of coordination complexes, when two identical ligands are adjacent to each other, it is referred to as the "cis" configuration, while when they are opposite each other, it is referred to as the "trans" configuration. Therefore, geometrical isomerism is indeed synonymous with cis-trans isomerism.

### Step 2: Analyze the Reason
- **Reason**: "Tetrahedral complexes show geometrical isomerism."
- **Explanation**: This statement is incorrect. Tetrahedral complexes do not exhibit geometrical isomerism. Instead, they can only show optical isomerism. In tetrahedral complexes, the arrangement of ligands around the central metal atom is such that the bond angles are approximately 109.5 degrees, and the distances between the ligands are similar. This means that there is no significant difference in spatial arrangement that would lead to geometrical isomers. Therefore, tetrahedral complexes cannot display geometrical isomerism.

### Step 3: Conclusion
- Since the assertion is true and the reason is false, the correct answer to the question is that the assertion is correct, but the reason is incorrect.

### Final Answer
- The assertion is true, and the reason is false.