单项选择题
A. Framing
B. De-encapsulation
C. Encapsulation
D. De-framing
E. None of the above
多项选择题 Regarding PAR (Positive Acknowledgement and Re-transmission), which of the answer choices below are correct?（）
单项选择题 Error detection schemes check errors in the data packets by reading which field frame IDs?（）
单项选择题 Which frame field do error detection schemes view to perform their function?（）