The correct answer is T1. A T1 line is a type of leased line, which uses a dedicated, point-to-point technology.

Sniffing is the action of capture the information going over the network.
Most popular way of connecting computers is through Ethernet. Ethernet protocol works by sending packet information to all the hosts on the same circuit. The packet header contains the proper address of the destination machine. Only the machine with the matching address is suppose to accept the packet. A machine that is accepting all packets, no matter what the packet header says, is said to be in promiscuous mode. Because, in a normal networking environment, account and password information is passed along Ethernet in clear-text, it is not hard for an intruder to put a machine into promiscuous mode and by sniffing, compromise all the machines on the net by capturing password in an illegal fashion.

When we encrypt data we are basically taking the plaintext information and applying some key material or keystream and conducting something called an XOR or Exclusive-OR operation. The symbol used for XOR is the following: This is a type of cipher known as a stream cipher.
The operation looks like this: 0101 0001 Plain text 0111 0011 Key stream 0010 0010 Output (ciphertext)
As you can see, it's not simple addition and the XOR Operation uses something called a truth table that explains why 0+1=1 and 1+1=0.
The rules are simples, if both bits are the same the result is zero, if both bits are not the same the result is one.
The following answers are incorrect:
-Bit Swapping: Incorrect. This isn't a known cryptographic operations.
-Logical NOR: Sorry, this isn't correct but is where only 0+0=1. All other combinations of 1+1, 1+0 equals 0. More on NOR here.
-Decryption: Sorry, this is the opposite of the process of encryption or, the process of applying the keystream to the plaintext to get the resulting encrypted text.
The following reference(s) was used to create this question: For more details on XOR and all other topics of cryptography. Subscribe to our holistic http://en.wikipedia.org/wiki/Exclusive-or and http://en.wikipedia.org/wiki/Stream_cipher