Step 1: Understand who can file a complaint under the Consumer Protection Act.
The Consumer Protection Act allows a wide range of complainants to file cases, including consumers who are directly affected, the State Government, or the Central Government on behalf of consumers.
Step 2: Evaluate the options.
- Any consumer who is affected by unfair trade practices can file a complaint.
- Both the State and Central Governments have the authority to file cases on behalf of consumers to protect public interests.
Step 3: Conclude.
The correct answer is that the complainant can be a consumer, state government, or central government.
Final Answer:
\[
\boxed{\text{All of these}}
\]