Which of the following can be considered as a cultural barrier to trade?

a. Prohibition on Zimbabwean aircrafts from flying over or landing in Canada
b. Restriction on the export of luxury goods to the Democratic Peoples Republic of Korea from Canada
c. An arms embargo imposed on China by the U.K. government
d. Japanese law requiring a new retail firm to receive permission from other retailers in the area in order to open a business
e. Restriction on the export of strategic goods to Ghana imposed by the government of U.K

d