Question

The secret of ____________ was discovered and perfected in china, and for hundreds of years potters elsewhere failed to duplicate it. terra cotta porcelain stained glass gold leaf

Answer 1

The correct answer is porcelain.
You may have seen in many movies Chinese porcelain, usually coming from the Ming dynasty. In those movies, you can see how important and valuable that porcelain is because everyone is extremely careful around it so as not to break it.