Which two statements are true about the rendezvo us point (RP) in a multicast network?（）
A. The multicast sources must register with the RP to form the multicast distribution tree.
B. An RP is required only in networks running Protocol Independent Multicast dense mode (PIM DM).
C. The mu lticast receivers must register with the RP to form the multicast distribution tree.
D. An RP is required only in networks running Protocol Independent Multicast sparse mode (PIM SM).
E. An RP is required only in networks running Protocol Independent Mu lticast sparse - dense mode (PIM - SDM).
F. To form the multicast distribution tree, the multicast sources register with and the receivers join the R
联合国体系下有关国际技术贸易的法律文件中有法律约束力的是（）。
A. 《联合国海洋法公约》
B. 《国际技术转让行动守则（草案》
C. 《人类环境宣言》
D. 《建立国际经济新秩序宣言》
何谓只读存储器ROM？有何功能特点？试述ROM、PROM、EPROM、EEPROM的本质区别？
He checked in late, （） he didn’t get a window seat.
A. that
B. so that
C. until
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