The X Bar chart must be used with either the R (range) chart or the s (standard deviation) chart depending on the c circumstances. So the instructions should read to choose between either an X-Bar and R chart or an X Bar and s chart. The fundamental question that you want to address is how to know when to use one or the other, or if it matters and why.
So think about the discussion question in terms of the amount and frequency of data that would be needed to determine the desired results and the probability that homogeneous (apples only) subgroups can be collected.