If `A sub B`, then `A cap B = ?`

Options

A. `phi`
B. A
C. B
D. None of these

Answer

To solve the problem, we need to determine what \( A \cap B \) (the intersection of sets A and B) is given that \( A \subseteq B \) (A is a subset of B).

### Step-by-Step Solution:

1. **Understanding the Definition of Subset**:
- Since \( A \subseteq B \), it means that every element of set A is also an element of set B. There are no elements in A that are not in B.

2. **Understanding Intersection**:
- The intersection of two sets, denoted as \( A \cap B \), is defined as the set of elements that are common to both sets A and B.

3. **Applying the Definition**:
- Since all elements of A are in B (because A is a subset of B), the common elements between A and B will be all the elements of A.

4. **Conclusion**:
- Therefore, \( A \cap B = A \).

### Final Answer:
- \( A \cap B = A \)