How many elements may the attributive clause be missing? Which relative word is missing from each component? How to choose relative words? Please speak simply, clearly and accurately.

Attributive clauses may lack subject, object, predicative, attributive, adverbial, subject, object and predicative, so when choosing which, who whom, That attributive, who adverbial, when where why ... when choosing related words, look at the sentence components of antecedents and clauses.