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NAT operation is typically transparent to both the internal and external hosts. Typically the internal host is aware of the true IP address and TCP or UDP port of the external host. Typically the NAT device may function as the default gateway for the internal host. However the external host is only aware of the public IP address for the NAT device and the particular port being used to communicate on behalf of a specific internal host. 
NAT and TCP/UDP 
"Pure NAT", operating on IP alone, may or may not correctly parse protocols that are totally concerned with IP information, such as ICMP, depending on whether the payload is interpreted by a host on the "inside" or "outside" of translation. As soon as the protocol stack is traversed, even with such basic protocols as TCP and UDP, the protocols will break unless NAT takes action beyond the network layer. IP packets have a checksum in each packet header, which provides error detection only for the header. IP datagrams may become fragmented and it is necessary for a NAT to reassemble these fragments to allow correct recalculation of higher-level checksums and correct tracking of which packets belong to which connection. The major transport layer protocols, TCP and UDP, have a checksum that covers all the data they carry, as well as the TCP/UDP header, plus a "pseudo-header" that contains the source and destination IP addresses of the packet carrying the TCP/UDP header. For an originating NAT to pass TCP or UDP successfully, it must recompute the TCP/UDP header checksum based on the translated IP addresses, not the original ones, and put that checksum into the TCP/UDP header of the first packet of the fragmented set of packets. The receiving NAT must recompute the IP checksum on every packet it passes to the destination host, and also recognize and recompute the TCP/UDP header using the retranslated addresses and pseudo-header. This is not a completely solved problem. One solution is for the receiving NAT to reassemble the entire segment and then recompute a checksum calculated across all packets. 
The originating host may perform Maximum transmission unit (MTU) path discovery to determine the packet size that can be transmitted without fragmentation, and then set the don't fragment (DF) bit in the appropriate packet header field. Of course, this is only a one- way solution, because the responding host can send packets of any size, which may be fragmented before reaching the NAT.

Multicast is a networking protocol where one host can send a message to a special multicast IP address and one or more network devices can listen for and receive those messages. 
Multicast works by taking advantage of the existing IPv4 networking infrastructure, and it does so in something of a weird fashion. As you read, keep in mind that things are a little confusing because multicast was "shoe-horned" in to an existing technology. For the rest of this article, let's use the multicast IP address of 239.255.0.1.

HTTP uses TCP port 80. 
http://pentestlab.wordpress.com/2012/03/05/common-tcpip-ports/

S Static 
E EGP 
D EIGRP 
R RIP 
O OSPF 
Default Administrative distance of EIGRP protocol is 90 then answer is C. 

  

Default Distance Value TableThis table lists the administrative distance default values of the protocols that Cisco supports:
Route Source 
Default Distance Values 
Connected interface 
Static route 
Enhanced Interior Gateway Routing Protocol (EIGRP) summary route External Border Gateway Protocol (BGP) 
Internal EIGRP 
IGRP 
OSPF 
Intermediate System-to-Intermediate System (IS-IS) Routing Information Protocol (RIP) Exterior Gateway Protocol (EGP) 
On Demand Routing (ODR) 
External EIGRP 
Internal BGP 
Unknown*

The subnet mask of the TFTP server needs to be in the same subnet as the default gateway.

The Cisco Unified IP Phone uses CDP to communicate information such as auxiliary VLAN ID, per port power management details, and Quality of Service (QoS) configuration information with the Cisco Catalyst switch.

https://www.freeccnaworkbook.com/workbooks/ccna/configuring-inter-vlan-routing-router-on-a-stick

http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/15986-admin-distance.html

  

Standard Ethernet frame MTU is 1500 bytes. This does not include the Ethernet header and Cyclic Redundancy Check (CRC) trailer, which is 18 bytes in length, to make the total Ethernet frame size of 1518. In this document, MTU size or packet size refers only to Ethernet payload. Ethernet frame size refers to the whole Ethernet frame, including the header and the trailer. Baby giant frames refer to Ethernet frame size up to 1600 bytes, and jumbo frame refers to Ethernet frame size up to 9216 bytes. 
Reference: http://www.cisco.com/c/en/us/support/docs/switches/catalyst-4000-series-switches/29805-175.html

Static routing can be used to define an exit point from a router when no other routes are available or necessary. This is called a default route.