Rainfall below 800mm occurs in ____ district.
A) Kanchipuram
B) Chennai
C) Nilgiris
D) Coimbatore

Hint:
Rainfall can be defined as the amount of precipitation, in the form of rain. The moisture or water vapor is carried by the atmospheric turbulence and convection upward into air masses where they form clouds. This water vapor is eventually released by clouds as rain.

Complete Answer:
The state of Tamil Nadu has three distinct periods of rainfall. They are rainfall that occur due to the tropical cyclones that emerge in the neighborhood of the Andaman Islands during the month of October–November, advanced rainfall and the North-East monsoon during the months of October–December. The rainfall in the state of Tamil Nadu is due to the southwest trade winds which blow towards the northern hemisphere. The annual rainfall in the Tamil Nadu state is 907mm. The distribution of rainfall in the districts of Tamil Nadu varies. Very low rainfall is seen in the Coimbatore and Tiruppur district that is below 800mm. Low rainfall is seen in Namakkal, Karur, Thoothukudi, Erode, Dharmapuri, Madurai, Tiruchirapalli, Perambur, Krishnagiri districts that range from 800 to 1000 mm. Moderate rainfall is seen in Sivagangai, Thanjavur, Salem, Ramanathapuram, Pudukkottai, Virudhunagar, Dindigul, Theni, and Vellore districts with 1000 to 1200 mm. Therefore, option D: Coimbatore is the correct answer as very low rainfall is seen in Coimbatore district with below 800mm.

So, option D is the correct option.

Note:
High rainfall with the amount of 1200 to 1400 mm is observed in the Thirunelveli, Tiruvannamalai, and Kanyakumari districts of Tamil Nadu. Above 1400 mm of very high rainfall is seen in Kanchipuram, Chennai, Villupuram, Thiruvarur, Thiruvarur, Cuddalore, Nagapattinam, and Nilgiris district of Tamil Nadu.