IPv6 is short for "Internet Protocol Version 6". IPv6 is the "next generation" protocol designed by the IETF to ______ the current version Internet Protocol, IP Version 4 ("IPv4") .

A．substitution

B．swap

C．switchover

D．replace

SBS改性沥青的最大特点是使沥青的( )均有显著改善。

A．水稳定性
B．抗滑性
C．高温性能
D．低温性能