Q.__________ city is called as "Detroit of Asia".

The correct option is (a) first: Tamil Nadu ranks first in cement production.

Tamil Nadu, with abundant limestone reserves (the key raw material) and a large number of cement manufacturing units, ranks first among Indian states in total cement production. Cement is one of the state's important mineral-based industries.

…

Chennai is called the "Detroit of Asia" because of its major automobile manufacturing cluster.

Detroit in the USA is the historic hub of the American car industry, so any city with a comparable concentration of automobile production is nicknamed after it. Chennai and its industrial corridor host several leading car and commercial-vehicle makers and a wide network of auto-component suppliers, making it one of India's largest automobile manufacturing and export centres. This makes Chennai the "Detro …

Chennai is called the (b) Detroit of India.

Chennai is a major automobile manufacturing hub, home to plants of leading Indian and multinational car and commercial-vehicle makers along with a dense network of auto-component suppliers. Because this mirrors the role Detroit plays as the automobile capital of the United States, Chennai has earned the nickname 'Detroit of India'. The automobile cluster around Chennai is one of the most important industrial clusters of Tamil Nadu.

Why the others are wrong: …