The gate that can act as a building block for the digital circuits is

Options

A. `OR`
B. `NOT`
C. `AND`
D. `NAND`

Answer

To solve the question regarding which gate acts as a building block for digital circuits, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Digital Circuits**:
- Digital circuits are made up of logic gates that perform operations on binary inputs to produce binary outputs. The basic types of logic gates include AND, OR, NOT, NAND, NOR, XOR, and XNOR.

2. **Identifying Universal Gates**:
- Among the various logic gates, NAND and NOR gates are known as universal gates. This means that any other logic gate (AND, OR, NOT, etc.) can be constructed using just NAND or NOR gates.

3. **Defining the NAND Gate**:
- The NAND gate is a combination of an AND gate followed by a NOT gate. It outputs false only when all its inputs are true; otherwise, it outputs true.

4. **Defining the NOR Gate**:
- The NOR gate is a combination of an OR gate followed by a NOT gate. It outputs true only when all its inputs are false; otherwise, it outputs false.

5. **Conclusion**:
- Since both NAND and NOR gates can be used to create any other type of gate, they are referred to as universal gates. However, the question specifically asks for one gate that can act as a building block. The NAND gate is often highlighted for its versatility and ease of use in circuit design.

### Final Answer:
The gate that can act as a building block for digital circuits is the **NAND gate**.

---