The NHAI(National Highway Authority of India) was constituted in 1998. It is responsible for the development, maintenance and management of National Highways. So, option (c) is correct.

The correct answer is option 'C' - National Highway Authority of India (NHAI). Let's understand why NHAI is responsible for implementing highway projects in India.

Central Public Works Department (CPWD):
The CPWD is a government agency responsible for the construction and maintenance of public infrastructure projects in India. However, it primarily focuses on projects related to buildings, government offices, and housing. While CPWD may be involved in road construction projects, it is not the primary organization responsible for implementing highway projects.

State Public Works Department (SPWD):
The SPWD is a state-level government agency responsible for the construction and maintenance of public infrastructure within a specific state. Like the CPWD, the SPWD primarily focuses on various types of construction projects within the state, including roads and highways. However, the responsibility of implementing national highway projects falls under the jurisdiction of a different organization.

National Highway Authority of India (NHAI):
The NHAI is an autonomous agency under the Ministry of Road Transport and Highways in India. It is responsible for the development, maintenance, and management of national highways across the country. NHAI is specifically tasked with the implementation of highway projects, including the construction, expansion, and improvement of national highways.

NHAI plays a crucial role in ensuring the efficient and safe movement of vehicles on national highways. It undertakes various activities such as detailed project preparation, land acquisition, engineering design, construction, operation, and maintenance of highways. It also monitors the quality of construction and ensures compliance with safety standards.

NHAI has been instrumental in the development of India's road infrastructure, facilitating better connectivity and enhancing economic growth. Its projects involve the construction of new highways, widening of existing highways, construction of bypasses, flyovers, and bridges, and the implementation of various safety measures.

By entrusting the responsibility of highway projects to NHAI, the government ensures a specialized agency is dedicated to the development and management of national highways. This helps in efficient planning, execution, and maintenance of these vital transportation routes, benefiting the overall transportation network of the country.