The correct answer is: a) Kadapa and Kurnool.
Limestone is a sedimentary rock composed mainly of calcium carbonate (CaCO3). It is the most common sedimentary rock on Earth, and it is found in significant deposits in many parts of the world. Limestone is a crucial mineral for the cement industry, as it is the main ingredient in cement. Cement is a binding agent that is used to make concrete, which is a ubiquitous building material.
The districts of Kadapa and Kurnool in Andhra Pradesh are known for their rich deposits of limestone. The limestone in these districts is of high quality and is used to produce cement that is exported to many countries around the world.
The other options are incorrect because they do not contain districts in Andhra Pradesh that are known for their limestone deposits.