Some clones are obtained by:

Options

A. Tissue culture
B. Plant breeding
C. Irradiation
D. Genetic engineering

Explanation

**Step-by-Step Solution:**

1. **Understanding Clones**: Clones are organisms that are genetically identical to one another. They are derived from a single parent cell, which means they share the same genetic material.

2. **Analyzing the Options**:
- **Option 1: Tissue Culture**: This is a technique used to grow plants in a controlled environment from a small piece of tissue. It allows for the production of multiple genetically identical plants, hence producing clones.
- **Option 2: Plant Breeding**: This involves crossing different plant varieties to create a new variety. This process does not produce clones as the offspring will have genetic variations.
- **Option 3: Irradiation**: This refers to exposing organisms to radiation. It does not lead to cloning; instead, it can cause mutations and genetic changes.
- **Option 4: Genetic Engineering**: While this involves altering genetic material, it does not inherently produce clones. It can create genetically modified organisms but not clones in the traditional sense.

3. **Conclusion**: The only method that produces clones is tissue culture. Therefore, the correct answer is **Option 1: Tissue Culture**.

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