Which of the following is a colonial alga is

Options

A. Chlorella
B. Volvox
C. Ulothrix
D. Spirogyra

Explanation

To solve the question "Which of the following is a colonial alga?", we will follow these steps:

### Step-by-Step Solution:

1. **Understand the Types of Algae**:
- Algae can be classified into different body forms: unicellular, colonial, and filamentous.
- Unicellular algae consist of single cells, while colonial algae are made up of groups of cells that function together as a single organism.

2. **Identify Examples of Algae**:
- **Unicellular Alga**: An example is Chlamydomonas, which exists as single cells.
- **Colonial Alga**: An example is Volvox, which forms spherical colonies of numerous cells.
- **Filamentous Algae**: Examples include Chlorella, Eulothrix, and Spirogyra, which are made up of long chains or filaments of cells.

3. **Analyze the Options**:
- Look at the options provided in the question. Identify which one is known to be a colonial alga.
- Based on the knowledge of algae types, recognize that Volvox is the correct answer as it is a well-known colonial alga.

4. **Conclusion**:
- After evaluating the types of algae and their examples, we conclude that the correct answer to the question is the colonial alga, which is **Volvox**.

### Final Answer:
The colonial alga is **Volvox**.