The answer is actually B) Memory T. Memory T cells rapidly produce large numbers of effector T-cells when re-exposed to their antigens, which provides the immune system memory against past infections.
Sound is a form of Energy that produces a sensation of hearing in our ears.
Sound is produced as a result of vibration produced in a body.
Sound energy is transmitted from one place o other place by wave motion.
When a body vibrates, the particles of medium surrounding it starts vibrating about their mean position.
During vibration, they collide with the surrounding particle and transfer some energy to them.
They then start vibrating faster and transferring energy to the next surrounding particle. This process continues till the vibration reaches a person ear.
Thus, particles are an important factor in propagation of sound.
Sound cannot travel in vacuum.
It requires a medium to travel from one point to another.
A sound can travel in all medium, solids, liquids and gases as all of these have particles.
The speed of sound is highest in solids and lowest in gases as the inter molecular space is largest in gases and smallest in solids.
