Answer from cs61c-ce (aretha samuel 15797004) for Question 1
umm...i don't know, but i will say arrays and other complex data structures.  MIPS retrieves their addresses from memory and puts them into registers and after the done operations, stores the results into the memory, compilers try to keep the most frequently used variables in registers and places the rest in memory, using loads and stores to move variales between registers adn memory