Question Discussion & Solution

Hypertext transfer protocol (HTTP):

• HTTP is used to access data on the world wide web. HTTP functions as a combination of FTP and SMTP. HTTP uses the services of TCP port number 80. HTTP is a stateless protocol.
• HTTP prior to version 1.1 specified a non-persistent connection, while a persistent connection is a default.
• In a non-persistent connection, one TCP connection is made for each request/ response. The client opens a TCP connection and sends a request and server sends the response then closes the connection.

File Transfer Protocol (FTP):

• FTP stands for file transfer protocol. It is provided by TCP/IP for copying a file from one host to another. FTP can transfer a file through one of the following three modes: stream mode, block mode and compressed mode. Stream mode is the default mode.
• FTP uses two TCP connections one for data and another for control.

Simple Transfer Protocol (SMTP):

• SMTP is a push protocol, it can push the messages from the client to the server only.
• SMTP uses one TCP connection at a time

TELNET:

• TELNET is a client/ server application that allows a user to log on to a remote machine, giving the user access to the remote system.
• TELNET uses one TCP connection at a time.

Important Point:

Option 1 is not correct since HTTP might have more than one TCP connections for a single web page.

The correct answer is Sodium and potassium.

Key Points

• Sodium and Potassium metals are the two metals which are soft and can be cut with a knife.
  • Both belong to Alkali metals [first group of periodic table]
  • They are reactive metals.
  • As the atomic size increases down the group, so the force of attraction between the valence electron and nucleus decreases. 
  • Metallic bonds are not strong.
  • Potassium is softer than sodium.

Additional Information 

• Mercury- In a liquid state at room temperature, It is unique as a metal.
  • Mercury (Hg), also known as quicksilver.
  • Atomic Number- 80
• Zinc- Related to low Melting group.
  • Atomic Number- 30
  • Symbol- Zn
• Tin- It is a soft silvery-white metal with a bluish tinge.
  • Atomic Number- 50
  • Symbol- Sn

CONCEPT:

Nuclear reactor:

• In a nuclear reactor, the energy is generated by a nuclear fission reaction.
• In a nuclear reactor, there is a concrete chamber and in this concrete chamber, there is a steel vessel. In this steel vessel, the nuclear fission reaction takes place.
• Fuel rods: Fuel rods are placed inside the steel chamber.
  • These rods are made of fissionable material. Generally, fuel rods are made of uranium-235, thorium, etc.
• Moderator: It is used to decrease the speed of fast-moving neutrons.
• Control rods: These rods are placed between the fuel rods. It is used to control the chain reaction. Control rods are generally made of cadmium.
  • The nuclear reactors are controlled by means of control rods which are made of a strongly neutron-absorbent material such as boron or cadmium (Cd).
• Coolant: It is used to absorb heat produced during the reaction.

EXPLANATION:

• Moderators are used to slow down the neutrons in order to carry out effective nuclear fission and also absorb neutrons. 
• The main reason why heavy water is used as the moderator is that it captures less number of neutrons compared to normal water Hence, option 2 is the answer. 

The first letter in each group is obtained by adding five letters to the first letter of the previous group.

W + 5 = B, B + 5 = G, G + 5 = L, L + 5 = Q, Q + 5 = V

The second letter in each group is opposite to the first letter of that group according to their positional value.

W ↔ D, B ↔ Y, G ↔ T, L ↔ O, Q ↔ J, V ↔ E

The numbers in in each group are obtained by adding two and its multiple at each step respectively.

4 + 2 = 6, 6 + 4 = 10, 10 + 6 = 16, 16 + 8 = 24, 24 + 10 = 34

When the box will be constructed, the following symbols will be opposite to each other as shown below:

So, when the box will be constructed, the symbols O and K will be opposite to each other.

Hence, option 3) O and K is the correct answer.