Question

which of the following is the main causes of heavy rainfall in Tamilnadu during the winter

Answer 1

India climate is tropical monsoon type climate. 
India experiences Southwest monsoon and Northeast monsoon

The southwest monsoon is generally expected to begin around the beginning of June and fade   away by the end of September. The moisture-laden winds on reaching the   southernmost point of the Indian Peninsula, due to its topography,   become divided into two parts: the Arabian Sea Branch and the Bay of   Bengal Branch.

The period October to December is referred to as  Northeast Monsoon season over peninsular India. Earlier   this period  was also referred to as "Post-Monsoon Season" or "Retreating southwest  Monsoon Season".
Northeast Monsoon season is the major period of  rainfall activity over south peninsula, particularly in the eastern half  comprising of the meteorological subdivisions of Coastal Andhra  Pradesh, Rayalaseema and Tamilnadu-Pondicherry. For Tamilnadu this is  the main rainy season accounting for about 48% of the annual rainfall.  Coastal districts of the State get nearly 60% of the  annual rainfall  and the interior districts get about 40-50%  of the annual rainfall.   Normal date of onset of the northeast monsoon is around 20 October with a  deviation of about a week on either side.

Answer 2

You haven't given any options?