Refer to the given dichotomous key and select the correct option regarding P, Q, R, S and T.
I. (a) Genetic material is not enclosed in nucleus. - Go to II
(b) Genetic material is enclosed in nucleus. - Go to III
II. (a) Lacks cell wall. - P
(b) Possesses cell wall. - Q
III. (a) Unicellular organism - R
(b) Multicellular organism - Go to IV
IV. (a) Plant body is sporophytic and water is required for fertilisation. - S
(b) Plant body is sporophytic and water is not required for fertilisation. - T

Options

A. P is motile whereas Q is non-motile.
B. R could be yeast or Chlamydomonas.
C. Both S and T produce seeds for propagation of their species.
D. S could be Adiantum whereas T could be Riccia.

Explanation

To solve the question regarding the classification of organisms P, Q, R, S, and T based on the given dichotomous key, we will follow the steps outlined in the key:

### Step-by-Step Solution:

1. **Identify the Genetic Material**:
- The first question in the key asks if the genetic material is enclosed in a nucleus.
- If **not enclosed**, we proceed to step II.
- If **enclosed**, we proceed to step III.

2. **Step II - Prokaryotes**:
- Since we are considering the case where genetic material is **not enclosed** in a nucleus, we go to step II.
- In step II, we have two options:
- (a) If it **lacks a cell wall**, it is classified as **P** (this corresponds to **Mycoplasma**).
- (b) If it **possesses a cell wall**, it is classified as **Q** (this can correspond to **Bacteria**).

3. **Step III - Eukaryotes**:
- If the genetic material is **enclosed** in a nucleus, we proceed to step III.
- In step III, we have two options:
- (a) If it is a **unicellular organism**, it is classified as **R** (this could be a **Protist** or **Yeast**).
- (b) If it is a **multicellular organism**, we proceed to step IV.

4. **Step IV - Multicellular Organisms**:
- In step IV, we have two options:
- (a) If the plant body is **sporophytic and water is required for fertilization**, it is classified as **S** (this corresponds to **Pteridophytes**).
- (b) If the plant body is **sporophytic and water is not required for fertilization**, it is classified as **T** (this corresponds to **Angiosperms**).

### Summary of Classifications:
- **P**: Mycoplasma (lacks cell wall, prokaryote)
- **Q**: Bacteria (possesses cell wall, prokaryote)
- **R**: Protist or Yeast (unicellular eukaryote)
- **S**: Pteridophyte (sporophytic, requires water for fertilization)
- **T**: Angiosperm (sporophytic, does not require water for fertilization)