Keys are required for
(a) Phylogenetic classification
(b) Natural classification
(c) Identification of organism
(d) Both b and c

Options

A. Phylogenetic classification
B. Natural classification
C. Identification of organism
D. Both B and C

Answer

To solve the question regarding the requirement of keys in classification, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the role of keys in different types of classification: phylogenetic, natural, and identification of organisms.

2. **Defining Keys**: Keys are taxonomical aids used for the identification of organisms. They typically consist of a series of choices that lead the user to the correct name of a given organism.

3. **Analyzing Each Option**:
- **(a) Phylogenetic Classification**: This classification is based on evolutionary relationships and does not primarily rely on keys. Instead, it uses phylogenetic trees and genetic data.
- **(b) Natural Classification**: While natural classification groups organisms based on natural relationships, it does not specifically require keys for its formation. Keys may assist in identifying organisms within these classifications but are not essential for the classification itself.
- **(c) Identification of Organism**: Keys are specifically designed for the identification of organisms. They help users differentiate between species based on observable characteristics.
- **(d) Both b and c**: This option suggests that keys are required for both natural classification and identification, which is not entirely accurate since keys are not essential for natural classification.

4. **Conclusion**: Based on the analysis, keys are primarily required for the identification of organisms (option C). They are not necessary for phylogenetic or natural classification.

5. **Final Answer**: The correct option is **(c) Identification of organism**.