Which of these is an example of an adaptation?

B. A camel has two rows of eyelashes to keep sand out of its eyes.

Adaptation is a genetic change or mutation that helps an organism to survive in its environment. These genetic changes are passed on to the next generation of the organism, hence maintains the population of the species. An adaptation can be structural, that means adaptation is in the physical part of the organism and it can be behavioral, regulating the behavior of the organism towards the environment.

A camel has two rows of eyelashes to keep sand out of its eyes is a structural adaptation because it helps camel expel out sand entering the eyes, which is being blown along with wind in desert area.  

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when the displaced particles are perpendicular to the direction the wave travels, is called a transverse wave, whereas in longitudinal wave the displace practices are parallel to the direction of the wave.

in the given image:

first image shows - longitudinal wave

second image shows - transverse wave

third image shows - longitudinal wave

fourth image shows - longitudinal wave