Which of the following statements is true regarding transfer of heat through the process of convection?
(A) It takes place only in gases.
(B) Heat flows in upward direction only.
(C) Physical contact is not essential.
(D) Heat is transferred by vibrational motion of particles.

Correct option is B

The correct answer is
Convection:
The transfer of heat energy through the movement of molecules from one place to another within the same body is called convection.
• The air in contact with the earth rises vertically on heating in the form of currents.
• The heating of the air leads to its expansion. Its density decreases and it moves upwards.
• Continuous ascent of heated air creates vacuum in the lower layers of the atmosphere. As a comes down to fil the vacuum. This process of vertical heating of the atmosphere is known as convection.
Conduction:
The transfer of heat through the molecules of matter in any body is called conduction. Accomplished by transfer of heat from one part of the body to the other part of the same body and from one body to the other touching body. The flow continues till the temperature of both the objects becomes equal or the contact is broken. The conduction in the atmosphere occurs at the zone of contact between the atmosphere and the earth's surface.
However, this is a minor method of heat transfer in terms of warming the atmosphere since it only affects the air close to the earth's surface, This is because of the fact that the air is a poor conductor of heat. Hence Statement 1 is incorrect.