A errors of addition, omission, substitution or ordering derive from overgeneralization of language rules.

B a pronunciation error tends to “camouflage” errors which, in fact, belong to other language levels.

C distinguishing or identifying different levels of language errors is not always an obvious task.

D local errors should not worry teachers as they do not impede understanding of the message.

E global errors must be prevented, especially those related to oral language comprehension.