Final answer:
In Java, a character constant's value is represented in the Unicode character set, which is a universal standard that covers all characters for all writing systems.
Step-by-step explanation:
In Java, a character constant's value is its integer value in the Unicode character set. The correct answer is (b) Unicode. Unicode is a universal character encoding standard that assigns a unique number to every character, no matter what platform, program, or language. It's designed to cover all the characters for all the writing systems of the world, modern and ancient, making it the preferred choice in programming and computing in general. In contrast, ASCII (American Standard Code for Information Interchange) is limited to 128 characters and is essentially a subset of Unicode. EBCDIC (Extended Binary Coded Decimal Interchange Code) is an older character encoding used mainly by IBM systems, BCD (Binary Coded Decimal) encodes the 10 decimal digits, and Binary represents data in the binary number system.