Answer from cs61c-ee (Michael Shen 15963205) for Question 3
The drawback of polling  is that it can waste a lot of processor time because processors are a lot faster than I/O devices.  The processor will read the status of the I/O device many times because it is so much slower.  Many times I/O devices are doing nothing and the processor will have to devote resources to check that the I/O device is doing nothing.