How does vegetative propagation take place in Bryophyllum?
A. Leaf
B. Stem
C. Root
D. Pollen

Hint: Vegetative propagation is a process in which a new plant is produced by using the vegetative or somatic parts of the parent plant. The vegetative parts of the plant include stem, leaves, branches and roots.

Complete Answer:
Now, let us analyze each option one by one to find the correct answer.
- Option A: In Bryophyllum, small leaf buds arise at the edges of the leaf, which can be used to propagate new plants. The leaf bud gives rise to adventitious roots and shoots. So, option A is correct.
- Option B: Stem is a vegetative part, but in Bryophyllum, the stem is not able to propagate as efficiently as the leaf buds. Also, the shoots aren't modified enough to store food for the generation of new plants. So, option B is incorrect.
- Option C: In Bryophyllum, the roots are not able to give rise to shoot once they are detached from the plant. The roots are modified to store food in Bryophyllum. So vegetative propagation does not take place through roots. So, option C is incorrect.
- Option D: Pollen is a male gamete that requires a female gamete to give rise to a new plant. Pollen takes part in sexual reproduction in plants while vegetative propagation is method of asexual reproduction in plants. So, option D is incorrect.

So, the correct answer is option A) Leaf.

Note: Some examples of vegetative propagation can be given as:
- Rhizomes: Ginger
- Bulbs: Onion, garlic
- Tubers: Potato, dahlia
- Runners: Mint
- Leaves: Bryophyllum
- Suckers: Apple, banana