Design a 1-bit ALU using the smallest MUX possible
If you consider the table as a 4 input combinational circuit and try to derive an expression from the K-map you will get
$$Z_0 = cont_0'cont_1a_0'b_0'+cont_0a_0b_0'+cont_0 a_0'b_0+cont_1'a_0b_0$$

Now you can see the pattern with $a_0$ and $b_0$ so you can make a smaller circuit with a 4x1 MUX having $a_0$ and $b_0$ as selection bit.