The correct answer is: a) Guntur.
Guntur district has a total of 66 mandals. It is one of the most populous districts in Andhra Pradesh, with a population of over 4.5 million people. The district is located in the coastal region of Andhra Pradesh, and its headquarters is the city of Guntur.
East Godavari district has a total of 58 mandals. It is the second most populous district in Andhra Pradesh, with a population of over 4.3 million people. The district is located in the coastal region of Andhra Pradesh, and its headquarters is the city of Kakinada.
Chittoor district has a total of 64 mandals. It is the third most populous district in Andhra Pradesh, with a population of over 3.8 million people. The district is located in the Rayalaseema region of Andhra Pradesh, and its headquarters is the city of Chittoor.
Anantapur district has a total of 60 mandals. It is the fourth most populous district in Andhra Pradesh, with a population of over 3.7 million people. The district is located in the Rayalaseema region of Andhra Pradesh, and its headquarters is the city of Anantapur.
The other options are incorrect because they do not have the highest number of mandals in Andhra Pradesh.