Context: Unicode can be implemented by different character encodings. The most commonly used encodings are UTF-8, UTF-16 and the now-obsolete UCS-2. UTF-8 uses one byte for any ASCII character, all of which have the same code values in both UTF-8 and ASCII encoding, and up to four bytes for other characters. UCS-2 uses a 16-bit code unit (two 8-bit bytes) for each character but cannot encode every character in the current Unicode standard. UTF-16 extends UCS-2, using one 16-bit unit for the characters that were representable in UCS-2 and two 16-bit units (4 × 8 bits) to handle each of the additional characters.

Question: What are the most commonly used encodings of Unicode?
Answer: UTF-8, UTF-16 and the now-obsolete UCS-2

Question: What does UTF-8 use in terms of bytes? 
Answer: UTF-8 uses one byte for any ASCII character

Question: What type of code does UCS-2 use?
Answer: 16-bit code unit

Question: What does UTF-16 expand? 
Answer: UCS-2

Question: How are two 16-bit units used? 
Answer: (4 × 8 bits

Question: What are character encodings implemented by?
Answer: Unanswerable

Question: Which two encodings are now obsolete?
Answer: Unanswerable

Question: What did UCS-2 expand?
Answer: Unanswerable

Question: How many ASCII characters are used to make one UTF-8?
Answer: Unanswerable

Question: What system has a minimum of four bytes?
Answer: Unanswerable