C) Liberalisation
The process of removing barriers or restrictions on foreign trade and investment set by the government is known as Liberalisation.
The passage directly states: "Removing barriers or restrictions set by the government is what is known as liberalisation." Import Tax and Export Tax are types of trade barriers, not their removal. Industrialisation refers to industrial development. Examiners expect the exact term with its meaning.
Source: Chapter 4, Liberalisation of foreign trade and foreign investment policy.