Answer from cs61c-fx (maryam nili 13888544) for Question 2
because the value in $t0 is available only after the fourth stage of the first instruction in the dependence, which is too late for the input of the third stage of add. so even with forwarding we have to
stall one stage.
we can put a nop after lw to be able to use forwarding.
By adding a multiplexer to the input of the ALU and with proper controls,we can run pipelines at full speed.