The question asks to identify the INCORRECT statement regarding tropical and extra-tropical cyclones.

Statement Analysis

Option 1: Hurricanes in South Atlantic

Hurricanes are storms primarily found in the North Atlantic and Northeast Pacific. While extremely rare, storms originating in the South Atlantic have occurred (e.g., Hurricane Catarina in 2004). However, for general purposes, their absence is often considered accurate compared to other basins.

Option 2: Africa and Tropical Cyclones

Africa is indeed rarely impacted directly by hurricanes or typhoons. Storms crossing the Atlantic often weaken before reaching the continent. Typhoons occur in the Pacific Ocean, not the Atlantic.

Option 3: Western Margins Frequency

The frequency of tropical cyclones hitting the western margins of continents is generally low. This is due to factors like cooler ocean currents and atmospheric steering patterns.

Option 4: Extra-tropical Cyclone Formation

This statement is INCORRECT. Extra-tropical cyclones, also known as mid-latitude cyclones or temperate cyclones, form in the middle and high latitudes outside of the tropics. They are driven by temperature contrasts along weather fronts and can form in both the Northern and Southern Hemispheres.

Conclusion

The statement "Extra-tropical cyclones form only in the southern hemisphere" is factually wrong as these cyclones form in both hemispheres.