The correct answer is (b), Mars Express.
Mars Express is a European Space Agency (ESA) space probe orbiting Mars since 2004. It was the first probe to orbit the planet in more than a decade and the first to orbit Mars from a polar orbit. The probe’s main goals are to study the Martian atmosphere and climate, to search for evidence of water, and to investigate the planet’s geology and potential for life.
In March 2015, Mars Express detected a large amount of nitrogen in the Martian atmosphere. This finding was significant because nitrogen is a key element for life as we know it. The presence of nitrogen in the Martian atmosphere suggests that the planet may have once been more hospitable to life than it is today.
The other options are incorrect. Mangalyaan is an Indian Mars orbiter that was launched in 2013 and entered orbit around Mars in 2014. Phoenix Mars Lander was an American robotic spacecraft that landed on Mars in 2008. Curiosity Rover is an American robotic rover that landed on Mars in 2012.