The correct answer for this question is option 3: Earth`s rotation. The Coriolis effect is the apparent deflection of the path of an object moving in a rotating system, such as the Earth. As the Earth rotates, objects that move across its surface, such as air or ocean currents, appear to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Option 1, pressure gradient, is not directly related to the Coriolis effect. Pressure gradient refers to the difference in atmospheric pressure between two locations, which can determine the direction and strength of winds, but it does not cause the Coriolis effect.

Option 2, Earth`s axis of inclination, is also not the correct explanation for the Coriolis effect. The Earth`s axis of inclination, also known as its tilt, is responsible for seasonal variations but not for the Coriolis effect.

Option 4, Earth`s revolution, is also not the correct explanation. Earth`s revolution, or its orbit around the Sun, is important for determining the length of a year and the changing seasons, but it does not directly influence the Coriolis effect.

In conclusion, the Coriolis effect is caused by the rotation of the Earth.