The Supreme Court on Monday sought the Centre's response on a plea challenging the mandatory linking of mobile phones with Aadhaar.A bench of Justice A.K. Sikri and Justice Ashok Bhushan gave the Centre four-weeks time to respond.The court also gave time to the West Bengal government to amend it's petition questioning the linking of Aadhaar for giving of subsidy by the state's Labour Department. It observed: "how could state government challenge a law passed by the Centre?"The court said West Bengal Chief Minister Mamata Banerjee could challenge the Aadhaar law as an "individual" and a "citizen".However, it also observed that "this way Centre would start challenging the laws passed by the States".