Small insects such as water strider can walk on water due to which phenomenon (choose the best one)
A. Viscosity
B. Surface tension
C. Friction
D. None of these

Hint: The only possible way in which the insects can stand on the surface of water is that the gravitational force acting on them is being balanced by some other force. This force that balances the gravitational force is exerted by the water.

Complete answer:
We know that on every object on earth, the earth will exert a gravitational force of attraction that will pull the object towards itself. That is why when we stand on a surface of water, we sink in. However, there are some insects which can walk on water. Now, if we think about it, the only possible way in which the insects can stand on the surface of water is that the gravitational force acting on them is being balanced by some other force.

This force that balances the gravitational force is exerted by the water. This force comes into play due to the surface tension of the water. The molecules of a liquid exert forces of attraction on each other called cohesive forces. Therefore, when a body is placed on the surface of the liquid, the liquid exerts a force on the body. The force perpendicular to the length of the body per unit length of the body is called surface tension.

Therefore, small insects can walk on the surface of water due to surface tension of water.

Note: One may say that friction can also be the reason due to which the insects can walk on the surface of water, similar to how we walk on ground. It is true that friction also helps the insects to walk on the surface but to walk on the surface the insect must first be able to stand on the surface and this is done with help of surface tension. Hence, surface tension is the best reason for the above statement.