Based on RFC 4890, what is the ICMP type and code that should never be dropped by the firewall to allow PMTUD? 

Answer options:

A. ICMPv6 Type 1 Code 0 no route to host
B. ICMPv6 Type 1 Code 1 communication with destination administratively prohibited
C. ICMPv6 Type 2 Code 0 packet too big
D. ICMPv6 Type 3 Code 1 fragment reassembly time exceeded
E. ICMPv6 Type 128 Code 0 echo request
F. ICMPv6 Type 129 Code 0 echo reply

C