How did the power sharing became more effective after 1990

After 1990, India saw the rise of regional political parties. This was also the beginning of the era of coalition government at the Centre. Since no single party got a clear majority in the Lok Sabha, the major national parties had to enter into an alliance with many parties including several regional parties to form a government at the Centre. This led to a new culture of power sharing and respect for the autonomy of State Governments. Thus, federal power-sharing is more effective today than it was in the early years after the Constitution came into force.

the answer is:

c. economic output