Apical dominance is caused by

Options

A. Auxins
B. Gibberellins
C. Cytokinins
D. Abscissic acid

Answer

### Step-by-Step Solution:

1. **Understanding Apical Dominance**:
- Apical dominance refers to the phenomenon where the growth of the apical bud (the top bud of a plant) suppresses the growth of lateral buds (side branches). This ensures that the plant grows taller rather than wider.

2. **Role of Hormones**:
- Plant hormones play a crucial role in regulating growth and development. In the context of apical dominance, specific hormones are responsible for this phenomenon.

3. **Identifying the Hormones**:
- The primary hormone responsible for apical dominance is **auxins**. Auxins promote the growth of the apical bud and inhibit the growth of lateral buds.

4. **Contrasting Other Hormones**:
- **Cytokinins**: These hormones can counteract the effects of auxins. When applied, they can promote the growth of lateral buds even in the presence of an apical bud.
- **Gibberellins**: These hormones are not directly involved in apical dominance.
- **Abscisic Acid**: This hormone acts as a growth inhibitor and does not promote apical dominance.

5. **Conclusion**:
- Based on the role of these hormones, we conclude that apical dominance is primarily caused by **auxins**.

### Final Answer:
Apical dominance is caused by **auxins**.

---