单项选择题
A. group 3
B. group 1
C. group 5
D. group 7
单项选择题 Whataretheheadersizesforpoint-to-pointandmulti-pointGRE（alsoknownasmGRE）withtunnelkey？（）
单项选择题 Whichonesarethetwotypeofciphers？（）
单项选择题 WhichSSLprotocoltakesanapplicationmessagetobetransmitted，fragmentsthedataintomanageableblocks，optionallycompressesthedata，appliesaMAC，encrypts，addsaheader，andtransmitstheresultingunitinaTCPsegment？（）