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

A 4:2 encoder can be implemented using 2 AND gates. So, the correct answer is c. 2 AND gates.

Here's a step-by-step explanation:

1. An encoder is a combinational circuit that converts binary information from n input lines to a maximum of 2^n output lines. A 4:2 encoder has 4 input lines and 2 output lines.

2. The output lines of a 4:2 encoder generate the binary code corresponding to the input value.

3. The first AND gate is used to check if the first or second input line is active. If either of these lines is active, the output of the first AND gate will be high (1).

4. The second AND gate is used to check if the third or fourth input line is active. If either of these lines is active, the output of the second AND gate will be high (1).

5. The outputs of the two AND gates are then used as the two output lines of the 4:2 encoder. The binary code generated by these two output lines corresponds to the input value.