A. Selection of trees
B. Trees of typical height and development should be selected in crops covering the range of distribution to which the results are to be applied
C. Trees with abnormal defects such as fork, broken top, etc.
D. Separate sets of trees may be required for different methods of thinning, origin of crops, etc.
E. All of the above
The correct answer to the question: "Field work includes:" is "All of the above".