Enumerate three major causes that lead to the systematic occurre

Enumerate three major causes that lead to the systematic occurrence of errors in second language acquisition.
【正确答案】：（1）Interference from the mother tongue：Mother tongue interference is found at the level of pronunciation, morphology, syntax, vocabulary and meaning, and can be predicted by contrasting the grammatical or other systems of the native and target languages，
（2）Interlingual interference within the target language：Interlingual interference，or cross-association, occurs when the learner mixes rules and patterns of the target language and produce hybrid structures．
（3） Overgeneralization：The use of previously available strategies in new situations，i.e. the application of a particular pattern or rule of the target language in many other linguistic situations．