The correct answer is: A) Pathanamthitta
Pathanamthitta is the smallest district of Kerala in terms of area. It has a total area of 1,783 square kilometers. The district is located in the central part of Kerala and is bordered by the districts of Alappuzha, Kottayam, Idukki, and Thrissur. The district is home to the Sabarimala Ayyappa Temple, one of the most popular pilgrimage sites in India.
The other options are incorrect because they are not the smallest districts of Kerala in terms of area. Alappuzha has a total area of 2,134 square kilometers, Kottayam has a total area of 2,494 square kilometers, and Kollam has a total area of 2,700 square kilometers.