Longitudinal strain is possible in
A. Liquid
B. Gases
C. Solid
D. All of these

Hint: The longitudinal strain is associated with length of a body. Only solids do have a property of rigid structure and definite size, length and shape and can change their length when a force is applied. The longitudinal strain also depends on the original length and the length decreased or increased due to elasticity.

Complete answer:
Depending on the nature of deformation,strain can be defined in three types. They are longitudinal strain, volumetric strain and shearing strain. Longitudinal strain is defined as the change in length per unit original length of the body. If \[l\] is the change in length and \[L\] is the original length of the body, then the longitudinal strain is given by \[\varepsilon = \dfrac{l}{L}\].
Since, the longitudinal strain is associated with the original length and the changed length; this property should only be possessed by solids. Solids have definite shape and size and can stretch in length due to the force applied. This is because molecules are closely packed to each other and the molecular positions are rigidly fixed. In liquids and gases, molecules are comparatively less closely packed and therefore the molecular positions are not rigidly fixed. Therefore, they do not have a fixed size and shape. Thus, longitudinal strain is only possible in solids and not possible in liquids and gases.

So, the correct answer is “Option C”.

Note:
Solids are very rigid and they resist any attempt to change their shape.
They do yield to force but return to their original position as soon as the force is removed.
Therefore, in order to stretch the solid and subject them to longitudinal strain the force applied must be very strong.