Which of the following categories is at the top of the classification hierarchy?
(a) Order
(b) Class
(c) Family
(d) Phylum

Options

A. Order
B. Class
C. Family
D. Phylum

Explanation

To determine which of the given categories is at the top of the classification hierarchy, we need to understand the taxonomic hierarchy in biological classification.

1. **Understanding Taxonomic Hierarchy**: The classification hierarchy is a system used to organize and categorize living organisms. It consists of several levels, starting from the broadest category to the most specific.

2. **Levels of Classification**: The main levels of classification, from the highest to the lowest, are:
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species

3. **Analyzing the Options**:
- (a) Order: This is a lower category in the hierarchy, coming after Class.
- (b) Class: This is also a lower category, coming after Phylum.
- (c) Family: This is even lower, coming after Order.
- (d) Phylum: This is higher than Class, Order, and Family.

4. **Conclusion**: Among the options provided, Phylum is the highest category. However, it is important to note that the absolute highest category in the classification hierarchy is Domain, which is not listed in the options.

Thus, the correct answer to the question is:
**(d) Phylum**