Which of the following is not among the four public sector units conferred with 'Maharatna Status' by the government?

The Union government on May 21, 2010 formally conferred the coveted maharatna status on four state-run companies  - Steel Authority of  India  Limited  (SAIL), National Thermal Power Corporation (NTPC),  Indian Oil Corporation  (IOC) and Oil and  Natural Gas Corporation (ONGC) - granting them a higher level of financial and managerial autonomy. The status empowers them to make foreign investments of up to Rs 5,000 crore on their own. The Maharatna status is granted to listed navaratna central public sector companies with an average annual turnover of more than Rs 25,000 crore, net profit after tax of Rs 5,000 crore and net worth of Rs 15,000 crore during the past three years. Company Coal India Ltd was also a contender for the Maharatna status, but could not make it for not being listed on the stock exchange.