Nios II Assembly, https://cpulator.01xz.net/?sys=nios-de10-lite :

Suppose we have the following code to call a function foo movi r12, 4 movi r18, 6 movi r20, ex5555 call foo add r22, r12, r18 r22, r22, r20 xor Which registers will we have to save before the call foo instruction? Select one or more a. r12 b. r18 c. r22 d. r20