Fill in the blank with the most appropriate option:

The boat will _____ when we walk on it in quiet water.

There is always an equal (in size) and opposite (in direction) reaction to every action. When one body applies a force to another, the second body applies an equal and opposite force to the first.Natural forces are always found in pairs. It is not possible to have a single isolated force.

In this scenario, the third law of motion applies. Every action has an equal and opposite reaction, according to the third rule of motion. 

The boat receives an equal and opposite reaction force when we step on it. 

Because the quiet water provides no resistance, the boat will go backwards.

Hence, The boat will move backwards when we walk on it in quiet water.