ALU

please help me understand how to do this, why are there two values for the inputs. why a1 and a0 for A?

1. Using 2-bit (1-selector) multiplexors and 1-bit Adders, build a 2-bit ALU as described by the figure (with Carryout and zero output signals) which performs the functions in each table. Numbers are in two's comple- ment form. Note: There is no Carryin signal. C1 Co Operation Carry_out2-bit ALU Control 01 A-EB 10 A+HB 11 A XOR B Result- Zero