The correct answer is: b) Transmission of high-voltage electricity.
APTRANSCO is a state-owned transmission company in Andhra Pradesh, India. It is responsible for the transmission of high-voltage electricity from generating stations to distribution companies. The company has a network of over 10,000 kilometers of transmission lines.
Option a) is incorrect because power generation is the responsibility of generating companies. Option c) is incorrect because distribution of electricity to consumers is the responsibility of distribution companies. Option d) is incorrect because regulation of the power sector is the responsibility of the government.