A slide under microscope shows following features:
(i) Unicellularity
(ii) Well defined nucleus
(iii) Biflagellate-one flagellum lying longitudinally and the other trannsversely
what would you identify it as?

Options

A. Protozoan
B. Bacterium
C. Euglenoids
D. Dinoflagellate

Explanation

To identify the organism based on the features observed under the microscope, we can follow these steps:

### Step-by-Step Solution:

1. **Examine Unicellularity**: The organism is unicellular, meaning it consists of a single cell. This is an important characteristic that helps narrow down the classification.

**Hint**: Remember that unicellular organisms can be either prokaryotic or eukaryotic.

2. **Identify the Nucleus**: The presence of a well-defined nucleus indicates that the organism is eukaryotic. Eukaryotic cells have a membrane-bound nucleus, while prokaryotic cells do not.

**Hint**: Consider the differences between eukaryotic and prokaryotic cells when identifying the organism.

3. **Analyze Flagella**: The organism is described as biflagellate, meaning it has two flagella. One flagellum is oriented longitudinally, and the other transversely. This specific arrangement is characteristic of certain groups of organisms.

**Hint**: Think about which types of organisms have a specific arrangement of two flagella.

4. **Identify the Group**: Based on the characteristics of being unicellular, having a well-defined nucleus, and being biflagellate, the organism can be identified as a dinoflagellate. Dinoflagellates are known for their unique flagella arrangement and are eukaryotic.

**Hint**: Recall that dinoflagellates are often found in aquatic environments and can be a type of algae.

### Final Identification:
The organism observed under the microscope can be identified as a **dinoflagellate**.