Refer to the passage.

It is my intention to curb the size and influence of the federal establishment and to demand recognition of the distinction between the powers granted to the federal government and those reserved to the states or to the people. All of us need to be reminded that the federal government did not create the states; the states created the federal government.

–President Ronald Reagan,
First inaugural address,
January 20, 1981

Which of the following scenarios would most likely have been opposed by the Republican Party during the Reagan administration?

A member of Congress introduces a bill to reduce tax rates for all income groups.
The AARP lobbies for the expansion of Medicare to cover more people and provide more services.
A coalition of governors requests that Congress change a federal welfare program from a categorical grant to a block grant.
The president proposes a budget that reduces federal spending on education and health care, areas traditionally controlled by state governments.

President Reagan and indeed most Republicans advocate for more power to be shifted to the State government. This means a reduction in federal influence in areas traditionally controlled by States.

Health is one of those areas so in lobbying the federal government to expand Medicare to cover more people and provide more services, the AARP is asking the FG to extend its control more into state controlled areas which is why President Reagan would most likely oppose it.