Ferrel`s law is a concept in meteorology that describes the deflection of wind and ocean currents in the Earth`s atmosphere. It is named after William Ferrel, an American meteorologist who developed the concept in the 19th century.

According to Ferrel`s law, the deflection of wind and ocean currents is influenced by the rotation of the Earth. In the Northern Hemisphere, wind and currents are deflected to the right, while in the Southern Hemisphere, they are deflected to the left. This phenomenon is known as the Coriolis effect.

Option 1, cold air-mass, is not the correct answer because Ferrel`s law is not specifically related to the deflection of cold air-masses. Rather, it applies to wind and ocean currents in general.

Option 2, hot air-mass, is also not the correct answer for the same reason mentioned above.

Option 3, monsoon air-mass, is not the correct answer because Ferrel`s law does not specifically pertain to the deflection of monsoon air-masses. It is a broader concept that applies to all types of wind and ocean currents.

The correct answer is option 4, trade wind and ocean currents. Ferrel`s law is indeed related to the