Micropropagation can be achieved by

The correct option is Tissue culture.

Step-by-step Explanation:

1. Understanding Micropropagation:
Micropropagation is a modern plant tissue culture technique used to rapidly multiply stock plant material to produce a large number of progeny plants (clones). It involves growing plant cells, tissues, or organs in an artificial, nutrient-rich sterile medium under controlled environmental conditions.

2. Analyzing the Options:
- Self-pollination: This is a sexual reproduction process occurring in flowers where pollen is transferred from the anther to the stigma of the same flower or another flower on the same plant. It does not involve laboratory-scale micro-cloning.
- Asexual reproduction: While micropropagation is a form of asexual reproduction, "asexual reproduction" is a very broad biological category that includes fission, budding, fragmentation, etc. It is not the specific technique used to achieve micropropagation.
- Tissue culture: This is the specific laboratory technique that provides the sterile, nutrient-rich environment (containing agar, sucrose, inorganic salts, vitamins, and plant growth regulators like auxins and cytokinins) necessary for micropropagation to occur. Thus, micropropagation is practically achieved through plant tissue culture.
- Vegetative propagation: This is a natural or traditional artificial method of asexual plant reproduction (like grafting, cutting, or layering). Micropropagation is sometimes called "micro-vegetative propagation," but it is specifically executed using in vitro tissue culture techniques.

3. Conclusion:
Since micropropagation relies entirely on growing small plant samples (explants) in a test tube or petri dish under aseptic conditions, it is achieved directly through the process of tissue culture.