Refer to the given d ichotomous key. Identify P -T and select the correct statement regarding them.
I. (a) It is a unicellular organism. - Go to II
(b) It is a multicellular organism. - Go to IV
II. (a) It possesses well organised nucleus. - Go to III
(b) It lacks well organised nucleus. - P
III. (a) Nutrition is parasitic. - Q
(b) Nutrition is mixotrophic. - R
IV. (a) It possesses chlorophyll. - S
(b) It lacks chlorophyll. - T

Options

A. P could be slipper animalcule.
B. R could be Euglena which possesses cilia that help in movement.
C. Q could be Plasmodium which causes malaria or it could be entamoeba which causes amoebic dysentery in humans.
D. S could be an alga li ke chlamydomonas whereas T could be a scavenger like vulture or a decomposer like Giardia.

Explanation

To solve the question using the given dichotomous key, we will identify the organisms P, Q, R, S, and T step by step.

### Step-by-Step Solution:

1. **Identify P**:
- The first question in the dichotomous key asks if the organism is unicellular or multicellular.
- Since P is identified under the option "It lacks well-organized nucleus," we conclude that P is a **prokaryotic organism**.
- Prokaryotic organisms are typically unicellular. Therefore, P could be a type of bacterium, such as **E. coli** or **Streptococcus**.

2. **Identify Q**:
- Q is reached after determining that the organism possesses a well-organized nucleus and has parasitic nutrition.
- This indicates that Q is a **eukaryotic organism** that is a parasite.
- A well-known example of this is **Plasmodium**, which causes malaria.

3. **Identify R**:
- R is reached after determining that the organism possesses a well-organized nucleus and has mixotrophic nutrition.
- Mixotrophic organisms can perform both autotrophic (photosynthesis) and heterotrophic (feeding on other organisms) nutrition.
- An example of R could be **Euglena**, which has chlorophyll and can photosynthesize but also feeds on organic material.

4. **Identify S**:
- S is reached after determining that the organism is multicellular and possesses chlorophyll.
- This indicates that S is likely a **plant** or an alga.
- A common example of S could be **Chlamydomonas**, which is a unicellular green alga but can also represent multicellular algae.

5. **Identify T**:
- T is reached after determining that the organism is multicellular and lacks chlorophyll.
- This indicates that T could be a **fungus** or an animal.
- An example of T could be a **vulture**, which is a scavenger bird that does not have chlorophyll.

### Summary of Identifications:
- P: Prokaryotic organism (e.g., E. coli)
- Q: Plasmodium (causes malaria)
- R: Euglena (mixotrophic)
- S: Chlamydomonas (alga)
- T: Vulture (multicellular, lacks chlorophyll)

### Correct Statement:
The correct statement regarding these organisms is that Q (Plasmodium) is a parasite causing disease, while P (E. coli) is a prokaryotic organism.