What action will be taken by a Cisco IOS router if a TCP packet, with the DF bit set, is larger than the egress interface MTU?

What action will be taken by a Cisco IOS router if a TCP packet, with the DF bit set, is
larger than the egress interface MTU?

A.
Split the packet into two packets, so that neither packet exceeds the egress interface
MTU, and forward them out.

B.
Respond to the sender with an ICMP Type 3 , Code 4.

C.
Respond to the sender with an ICMP Type 12, Code 2.

D.
Transmit the packet unmodified.