Nations that pioneered normalization in the treatment of intellectual disability include:

A) the United States and Canada.
B) the former Soviet Union and China.
C) Japan and Great Britain.
D) Denmark and Sweden.

Normalization

The principle that institutions and community residences should provide people with intellectual disability types of living conditions and opportunities that are similar to those enjoyed by the rest of society.

Denmark And Sweden

Two distinct Northern European countries known for their rich history, cultural heritage, and contributions to arts, science, and governance.