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.

A.DHCP clients will automatically default to the DNS root servers for all DNS requests in the IP stacks locally. 
B.DHCP clients will use the IP set in the option 150 command.
C.DHCP clients will use the DNS entry assigned by the ISP.
D.DHCP clients will have no DNS server set in the IP stack.