جواب السؤال 22 في اسئلة سحاب الليل :
22- To constitute a proper variable , a good categorization\classification system ....................
A. Should be exhaustive.
B. Should have mutually exclusive categories.
C. Should not mix categories of different types in one set.
D. All the above.
الخيار موجود B بس الجواب الصحيح D