Read the passage carefully and choose the best option A, B, C or D to answer

The American education system requires that students complete 12 years of primary and secondary education prior to attending university or college. This may be accomplished either at public or government-operated schools, or at private schools. These 12 years of schooling or their equivalent may also be completed outside the USA, thus giving foreign students the opportunity to pursue the benefits of the American education system and obtain a quality American education. Perhaps one of the most impressive facts is that a large number of presidents, prime ministers and leaders from other countries have experienced the American education system and graduated from a university or school in the USA. In many fields and industries, the American education system offers the most cutting-edge, sought-after programs at the world's best schools. That is why graduating from an accredited American school and being exposed to the rigors of the American education system is an investment in your future.

Whether you want to study at a top USA university, a top USA college, a vocational or high school, a thorough understanding of how the American education system works is essential. Without a clear grasp of the American education system, an international student will find it difficult to make the right academic choices. It is no surprise that the American education system and the American school system host more international students than any other country in the world!

The expression government-operated could best be replaced by _______.

• A. 
  state
• B. 
  independent 
• C. 
  boarding
• D. 
  vocational