Dalton's atomic theory successfully explained.
(i) Law of conservation of mass (ii) Law of constant composition
(iii) Law of radioactivity (iv) Law of multiple proportion

Options

A. (i), (ii) and (iii)
B. (i), (iii) and (iv)
C. (ii), (iii) and (iv)
D. (i), (ii) and (iv)

Explanation

To answer the question regarding which laws Dalton's atomic theory successfully explained, we can analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Dalton's Atomic Theory**:
- Dalton proposed that matter is composed of indivisible atoms. He stated that all atoms of a given element are identical in mass and properties, and different elements have atoms with different masses and properties.

2. **Law of Conservation of Mass**:
- This law states that mass is neither created nor destroyed in a chemical reaction. Dalton's theory supports this law because if atoms are rearranged during reactions but not created or destroyed, the total mass before and after the reaction remains the same.

3. **Law of Constant Composition**:
- This law states that a chemical compound always contains the same proportion of elements by mass. Dalton's theory explains this because it posits that compounds are formed from specific combinations of atoms, which maintain consistent ratios.

4. **Law of Radioactivity**:
- This law pertains to the behavior of unstable atomic nuclei and their decay. Dalton's atomic theory does not explain radioactivity, as it was proposed before the discovery of radioactivity and does not account for nuclear processes.

5. **Law of Multiple Proportions**:
- This law states that when two elements combine to form more than one compound, the ratios of the masses of one element that combine with a fixed mass of the other element are in simple whole-number ratios. Dalton's theory supports this law as it explains how different combinations of atoms can lead to different compounds.

### Conclusion:
Based on the analysis:
- Dalton's atomic theory successfully explained:
- (i) Law of conservation of mass
- (ii) Law of constant composition
- (iv) Law of multiple proportions
- It did not explain:
- (iii) Law of radioactivity

Thus, the correct answer is that Dalton's atomic theory successfully explained the first, second, and fourth statements.

### Final Answer:
The correct options are (i), (ii), and (iv).

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