The correct option is B curbing subversive and unconstitutional activities
The Fundamental Duties were included in the Constitution with the idea of curbing subversive and unconstitutional activities. Originally, there were no fundamental duties in the Constitution. They were added by 42nd and 86th Constitutional Amendment acts. As of now, there are 11 Fundamental duties. Citizens are morally obligated by the Constitution to perform these duties. They are not legally enforceable like fundamental rights.