Read the following statements :
I. IAA and IBA are natural auxins.
II. 2,4-D is a synthetic auxin used as herbicide.
III. Ethylene promotes root hair formation.
IV. 2,4-D is used for development of grass free dicot weed lawns.
Correct answer is :

Options

A. I, II, III
B. I, III, IV
C. II, III, IV
D. I, II, IV

Answer

To determine the correct statements about plant hormones and their roles, let's analyze each statement step by step.

### Step 1: Evaluate Statement I
**Statement I:** IAA and IBA are natural auxins.
- **Analysis:** IAA (Indole-3-acetic acid) and IBA (Indole-3-butyric acid) are indeed classified as natural auxins. They are plant hormones that play a crucial role in growth and development.
- **Conclusion:** This statement is **correct**.

### Step 2: Evaluate Statement II
**Statement II:** 2,4-D is a synthetic auxin used as herbicide.
- **Analysis:** 2,4-D (2,4-Dichlorophenoxyacetic acid) is a well-known synthetic auxin that is widely used as a herbicide to control broadleaf weeds.
- **Conclusion:** This statement is **correct**.

### Step 3: Evaluate Statement III
**Statement III:** Ethylene promotes root hair formation.
- **Analysis:** Ethylene is a plant hormone that is involved in various processes, including fruit ripening and response to stress. It does promote root hair formation, helping in the absorption of water and nutrients.
- **Conclusion:** This statement is **correct**.

### Step 4: Evaluate Statement IV
**Statement IV:** 2,4-D is used for the development of grass-free dicot weed lawns.
- **Analysis:** While 2,4-D is used as a herbicide, it is primarily effective against broadleaf weeds and can harm grasses. Therefore, it is not used for developing grass-free lawns but rather to eliminate unwanted dicot weeds.
- **Conclusion:** This statement is **incorrect**.

### Final Conclusion
Based on the evaluations:
- Statements I, II, and III are correct.
- Statement IV is incorrect.

Thus, the correct answer is that the first three statements are correct.