单项选择题

A.Use hash MD5 to ensure that IKE works through NAT. 
B.Use ah-sha-hmac, as it does not check the integrity of the IP header. The IP header will change due to NAT. 
C.Use 3DES, as it will encrypt the IPSec header IP addresses and bypass addressing issues. 
D.Use esp-sha-hmac, as it does not check the integrity of the IP header. The IP header will change due to NAT.