Final answer:
The correct synonym for 'type' when it refers to a model or perfect example is 'prototype'. Among the provided options, 'prototype' is the only one that fits this definition.
Step-by-step explanation:
The synonym for "type" in the sense of a model or perfect example is prototype. A prototype is an original model on which something is patterned or an early sample, model, or release of a product built to test a concept or process. Among the options provided, (a) prototype correctly aligns with this definition and is the best answer to this question. Options (b) class, (c) autocracy, and (d) undercurrent do not fit the context of a model or perfect example as intended in the question.