निम्नलिखित में से कौन सी परिघटना उस प्रक्रिया को दर्शाती है जिसमें ठोस अवस्था, द्रव अवस्था में बदले बिना सीधे गैसीय अवस्था में परिवर्तित हो जाती है?

Substances A and B together form C, and substances D and E together form F. The newly formed substances C and F have the following properties: (a) C exhibits the properties of both A and B. (b) D and E can be separated from F by electrochemical methods only. Which of the following statements is true?

Which of the following is considered a chemical change?