Consider the following statements:
1. Richter scale is used to measure the intensity of hurricanes.
2. In a cyclone, air circulation is counter-clockwise in the Northern Hemisphere.
3. Tropical cyclones are most common in the South Atlantic Ocean.
4. How many of the statements given above are correct?

Correct option is A

The Correct answer is(a) Only one
Explanation:
. Statement 1 is  incorrect. The  Saffir-Simpson scale is used to measure the intensity of hurricanes based on wind speed, while the Richter scale measures the magnitude of earthquakes.
. Statement 2 is  correct. Due to the Coriolis effect, air circulates inward in a  counter-clockwise (or anti-clockwise) direction around a low-pressure area (cyclone) in the Northern Hemisphere.
. Statement 3 is  incorrect. Tropical cyclones are extremely rare in the South Atlantic Ocean due to strong vertical wind shear and cooler water temperatures; it is not considered a formal tropical cyclone basin. 
Information Booster:
. The Saffir-Simpson Hurricane Wind Scale classifies hurricanes into 1 to 5 categories based on maximum sustained wind speed.
. The Coriolis force causes moving air and water to turn to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, dictating the rotation direction of large weather systems.
. The South Atlantic Ocean lacks the necessary conditions (specifically, consistent warm water and lack of wind shear) for frequent tropical cyclone formation; Hurricane Catarina in 2004 is the only recorded hurricane-strength tropical cyclone in that basin's history. 
Additional Knowledge:
Richter scale is used to measure the intensity of hurricanes. (Option a - first part of pair)
. The  Richter scale measures the magnitude (energy released) of an earthquake.
. The Modified Mercalli Intensity Scale measures the intensity of an earthquake's local effects and damage. 
Tropical cyclones are most common in the South Atlantic Ocean. (Option c - third part of pair)
. Tropical cyclones are most common in ocean basins like the Western North Pacific (typhoons) and the North Atlantic/Eastern Pacific (hurricanes), as well as the Indian Ocean and South Pacific (cyclones).
. The South Atlantic is the only tropical ocean stretch where tropical cyclones are a very rare occurrence.