Question

social security and medicare
are voluntary programs aimed specifically at the poor.
have had little effect on the health and income of older americans.
are the largest and most expensive social welfare programs in america.
require an income and means test for eligibility.
all of the above

Explanation:

Social Security and Medicare are not voluntary (so A is wrong), they have had a significant positive effect on older Americans (so B is wrong), and they don't require an income - means test (so D is wrong). They are indeed the largest and most expensive social welfare programs in the U.S.

Answer:

C. are the largest and most expensive social welfare programs in America.