Relationship between Cyclone and Anti-cyclone
Cyclones and anti-cyclones are two weather phenomena that occur on Earth. They are both characterized by the circulation of air masses, but in opposite directions. A cyclone is a low-pressure system in which air flows inward and upward, while an anti-cyclone is a high-pressure system in which air flows outward and downward.

Understanding the relationship
To understand the relationship between a cyclone and an anti-cyclone, we need to focus on their opposing characteristics. A cyclone is known for its destructive nature, with strong winds, heavy rainfall, and potential for damage. On the other hand, an anti-cyclone is associated with calm and stable weather conditions, often resulting in clear skies and fair weather.

Applying the relationship to the given pair
Now, let's apply the same relationship to the given pair of words - "Cyclone is related to Anti-cyclone; in the same way as Flood is related to __________."

Option a) Devastation
Devastation refers to the widespread destruction and damage caused by a calamity or disaster. While a flood can indeed result in devastation, it does not have the same direct opposite relationship as a cyclone and an anti-cyclone.

Option b) Havoc
Havoc is another word that describes widespread chaos, disorder, and damage. Similar to option a, havoc can be a consequence of a flood, but it does not represent the opposite or contrasting relationship that exists between a cyclone and an anti-cyclone.

Option c) River
A river is a natural watercourse that flows towards an ocean, sea, or lake. While floods often occur in rivers due to excessive rainfall or other factors, it does not represent the opposite or contrasting relationship to a cyclone and an anti-cyclone.

Option d) Drought
Drought is a prolonged period of abnormally low rainfall, leading to a shortage of water supply. This option represents the opposite relationship to a flood, just as an anti-cyclone represents the opposite of a cyclone. A flood is characterized by excessive rainfall and an overflow of water, while a drought is characterized by a lack of rainfall and a scarcity of water.

Therefore, the correct answer is option d) Drought, as it exhibits the same relationship as the given pair of words - "Cyclone is related to Anti-cyclone; in the same way as Flood is related to Drought."