Which of the following prefixes indicates 'different'?

The prefix that indicates 'different' is "hetero-." This prefix is commonly used in various medical and scientific terms to demonstrate diversity or variation among components. For example, in the term "heterosexual," it denotes different sexes, while in "heterogeneous," it describes a mixture consisting of different substances or compositions.

The other prefixes do not convey the meaning of 'different.' "Eu-" refers to something good or normal, "micro-" means small, and "mal-" signifies bad or abnormal. Therefore, "hetero-" is the correct choice, as its definition directly aligns with the notion of difference or variation.