The correct answer is option 'C' which is multiplication.

**AND Gate:**
An AND gate is a fundamental logic gate in digital circuits. It has two or more input signals and produces an output signal only if all the input signals are high (true). The output is low (false) if any of the input signals are low.

**Basic Application of AND Gate in Computers:**

**1. Boolean Logic:**
AND gates are commonly used in computers to perform Boolean logic operations. Boolean logic is the foundation of digital circuits and computer programming. The AND gate allows us to combine two or more binary inputs to produce a single output based on the logical AND operation.

**2. Multiplexers and Demultiplexers:**
Multiplexers and demultiplexers are digital circuits that are used in computers to select and route data between multiple sources and destinations. AND gates are used in these circuits to control the selection and routing of data based on specific conditions.

**3. Address Decoding:**
In computer memory systems, address decoding is used to select a specific memory location for read or write operations. AND gates are used in the address decoding circuitry to ensure that the correct memory location is accessed based on the address signals provided by the computer.

**4. Instruction Decoding:**
In a computer's instruction decoding stage, the instruction code is analyzed to determine the specific operation to be performed. AND gates are used in the decoding circuitry to check specific bits or combinations of bits in the instruction code and generate control signals accordingly.

**5. Arithmetic Logic Unit (ALU):**
The Arithmetic Logic Unit (ALU) is a key component of a computer's central processing unit (CPU). It performs arithmetic and logical operations on data. AND gates are used in the ALU to perform logical AND operations on binary data during operations like multiplication.

**Conclusion:**
The basic application of an AND gate in computers is not limited to multiplication, but it is also used in various other aspects such as Boolean logic, multiplexers, demultiplexers, address decoding, instruction decoding, and the Arithmetic Logic Unit (ALU). However, the option 'C' which is multiplication specifically highlights the operation where AND gates are extensively used.