The correct answer is option 1: Vegetative propagation. This is a type of asexual reproduction in plants where new individuals are formed without the production of seeds or spores. In Bryophyllum, buds are formed at the edges of the leaves that grow into new plants when they fall on suitable soil.

Option 2, Budding, is an incorrect answer because it refers to a form of asexual reproduction where a new organism grows out of the parent organism, which is common in yeasts and hydra.

Option 3, Spore formation, is also incorrect. While it is a type of asexual reproduction, it is not applicable to Bryophyllum. In this method, spores are produced in the parent, which grow into new individuals. This method is seen more in fungi and bacteria.

Option 4, Regeneration, is a process where an organism regrows a lost part of its body. It is not the correct method of reproduction for Bryophyllum.