Step 1: Historical Context
Before gaining independence in 1971, Bangladesh was known as East Pakistan. It was part of Pakistan after the partition of India in 1947, which created the separate nations of India and Pakistan. The nation of Pakistan consisted of two geographically separated regions: West Pakistan (modern-day Pakistan) and East Pakistan (modern-day Bangladesh).
Step 2: Analyzing the Options
- (A) Pakistan: Correct. Bangladesh, originally East Pakistan, became an independent country after the Bangladesh Liberation War in 1971.
- (B) China: Incorrect. Bangladesh was never part of China.
- (C) India: Incorrect. Bangladesh was not part of India, though it shares cultural and historical ties.
- (D) None of these: Incorrect. The correct answer is Pakistan.
Step 3: Conclusion
Bangladesh gained independence from Pakistan after the Liberation War, and it is now a separate sovereign nation. The correct answer is Pakistan.
\[
\boxed{\text{Correct Answer: (A) Pakistan}}
\]