51. Opcode Decoder

How do you plan to solve it?

module alu_decoder (
    input  [1:0] opcode,
    output reg [3:0] alu_op
);
    
    always @* begin
    //     case (opcode)
    //         2'b00 : al
    //     endcase
        alu_op = ( 4'b0001 << opcode ); 
    end
endmodule