In the United States from 2009 through 2018:

a) national health expenditures as a percent of gross domestic product and per capita national expenditures have remained relatively constant.

b) national health expenditures as a percent of gross domestic product and per capita national expenditures have increased.

c) national health expenditures as a percent of gross domestic product have remained relatively constant while per capita national health expenditures have increased.

d) national health expenditures as a percent of gross domestic product have increased while per capita national health expenditures have remained relatively constant.