Which of the following is reported to have found in march, 2015 biologically useful nitrogen on Mars?

Curiosity is the right answer. In March 2015, NASA scientists led by Jennifer Stern of Goddard reported in the journal Science that Curiosity's SAM (Sample Analysis at Mars) instrument had detected nitrates in sedimentary rocks at Gale Crater, especially in the Yellowknife Bay mudstone. Nitrates are a form of nitrogen that microbes can use, so the finding mattered for habitability, not just for geology.

• Mangalyaan (A): ISRO's Mars Orbiter Mission, launched in 2013 and in Mars orbit from 2014. Its instruments studied the atmosphere, including methane, not surface nitrogen compounds.
• Mars Express (B): ESA's orbiter, in service since 2003. Its well-known results concern water and ice, not this nitrogen detection.
• Phoenix Mars Lander (C): landed in 2008 in the northern plains, found water ice and perchlorates, and operated only for a few months. It did not report biologically useful nitrogen.

The core concept is Mars habitability: liquid water, energy, and bioessential elements such as carbon, nitrogen and phosphorus. For Mains GS III (science and technology, space), this shows how missions have moved from asking whether Mars had water to asking whether it had the chemistry life needs.

Trap: Aspirants often pick Mangalyaan because it is the Indian mission and the most publicised Mars mission of that period, but its science was about methane and the atmosphere.