A source generates four messages m1, m2, m3, and m4 with probabilities 0.5, 0.25, 0.125 and 0.125 respectively. The messages are generated independently of each other. A source coder assigns binary code to each message. Which of the following codes has minimum average length and is also uniquely decodable (sequence as per m1, m2, m3, m4)?

• A. 00, 01, 10, 11
• B. 0, 1, 10, 11
• C. 110, 111, 10, 0
• D. 0, 10, 110, 111