A 4:2 encoder can be implemented using a.1 AND gate and 1 OR gateb.2 OR gatesc.2 AND gatesd.2 NAND gates

The correct answer is c. 2 AND gates.

Here's the step by step explanation:

A 4:2 encoder has 4 input lines and 2 output lines. The output lines generate the binary code corresponding to the input value.

Step 1: The first AND gate is used to encode the first two inputs. If the first input is 1 and the second input is 0, the output of the first AND gate is 1.

Step 2: The second AND gate is used to encode the last two inputs. If the third input is 1 and the fourth input is 0, the output of the second AND gate is 1.

Step 3: The outputs of the two AND gates are then used as the two output lines of the encoder.

So, a 4:2 encoder can be implemented using 2 AND gates.