Which of the following statements is/are correct?

a. The natural basin around Vijayanagara was formed by the river Tungabhadra, which flows in a north-westerly direction. b. Abdur Razzaq, an ambassador sent by the ruler of Persia to Vijaynagara, was very impressed with the elaborate arrangements that had been made to store rainwater and conduct it to the city. c. One of the most prominent waterworks to be seen among the ruins is the Hiriya canal built by kings of the Sangama dynasty.