The correct answer is (a) 8 bits.
Unicode is a character encoding standard that assigns a unique number to every character, regardless of platform, device, application, or language. This allows computers to represent and process text in any language.
The size of Unicode is 8 bits, which means that each character is represented by a number from 0 to 255. This is enough to represent all of the characters in the ASCII character set, as well as many other characters from other languages.
Option (b) is incorrect because 4 bits is not enough to represent all of the characters in the ASCII character set. Option (c) is incorrect because 16 bits is not enough to represent all of the characters in Unicode. Option (d) is incorrect because 32 bits is more than necessary to represent all of the characters in Unicode.