Step 1: Recall what liberalisation means.
It is the process of cutting down government imposed restrictions on trade and investment so that businesses can operate more freely.
Step 2: Check the options against this idea.
Protecting domestic industries, banning foreign companies, and restricting foreign investment are all about adding restrictions, which is the opposite of liberalisation.
Step 3: Match the correct description.
Removing restrictions on trade fits the meaning of liberalisation exactly, since it opens up the economy instead of closing it off.
Hence, the correct answer is option (C), removal of restrictions on trade.