What happens when calcium is treated with water?
(i) It does not react with water. 
(ii) It reacts violently with water.
(iii) It reacts less violently with water. 
(iv) Bubbles of hydrogen gas formed stick to the surface of calcium.

Options

A. I and iv
B. ii and iii
C. I and ii
D. iii and iv

Explanation

### Step-by-Step Solution:

1. **Understanding Calcium's Reactivity with Water**:
- Calcium is an alkaline earth metal and is known to react with water.

2. **Identifying the Reaction**:
- When calcium (Ca) reacts with water (H₂O), it forms calcium hydroxide (Ca(OH)₂) and hydrogen gas (H₂).
- The balanced chemical equation for this reaction is:
\[ Ca + 2H_2O \rightarrow Ca(OH)_2 + H_2 \]

3. **Nature of the Reaction**:
- The reaction of calcium with water is less violent compared to other alkali metals. This means that it does not produce a large amount of heat or cause an explosive reaction.

4. **Hydrogen Gas Production**:
- During this reaction, hydrogen gas is produced. This gas forms bubbles that can stick to the surface of the calcium metal.

5. **Evaluating the Given Statements**:
- (i) It does not react with water. **(Incorrect)**
- (ii) It reacts violently with water. **(Incorrect)**
- (iii) It reacts less violently with water. **(Correct)**
- (iv) Bubbles of hydrogen gas formed stick to the surface of calcium. **(Correct)**

6. **Conclusion**:
- The correct statements regarding the reaction of calcium with water are (iii) and (iv). Therefore, the answer is that calcium reacts less violently with water and the hydrogen gas produced sticks to its surface.