The suffix -'oideae' is used for

Options

A. tribe
B. family
C. class
D. subfamily.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the suffix '-oideae' and what it signifies in biological classification.

2. **Identifying the Options**: The options provided are tribe, family, class, and subfamily.

3. **Recalling Biological Nomenclature**: In biological classification, different suffixes are used to denote various taxonomic ranks. For example, '-aceae' is commonly used for families, while '-oideae' is specifically used for subfamilies.

4. **Analyzing the Suffix '-oideae'**: The suffix '-oideae' is a standard suffix used in the classification of plants and other organisms to indicate a subfamily.

5. **Providing Examples**: Examples of subfamilies that use the suffix '-oideae' include Krenidoi and Kenoidea, which further illustrate the application of this suffix in naming.

6. **Conclusion**: Based on the understanding of biological nomenclature and the specific use of the suffix '-oideae', we can conclude that it refers to a subfamily.

7. **Final Answer**: The correct option is **subfamily** (Option D).

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