`{:(,"Column A",,,"Column B"),(A.,"Efflorescent",(),a.,"Cobalt chloride"),(B.,"Deliquescent",(),b.,"Sodium chloride"),(C.,"Hygroscopic",(),c.,"Zinc chloride"),(D.,"Food additive",(),d.,"Mercuric nitrate"),(,,(),e.,"Washing soda"):}`

Explanation

To solve the matching question between Column A and Column B, we will analyze each term in Column A and find the corresponding example from Column B.

### Step-by-Step Solution:

1. **Understanding Efflorescent:**
- Efflorescent substances are those that lose water of crystallization when exposed to air.
- **Example:** Washing soda (Na2CO3·10H2O) is an efflorescent substance because it loses water when exposed to air.
- **Match:** A. Efflorescent → e. Washing soda

2. **Understanding Deliquescent:**
- Deliquescent substances absorb moisture from the atmosphere until they dissolve and form a solution.
- **Example:** Zinc chloride is a deliquescent substance as it absorbs moisture and can turn into a solution.
- **Match:** B. Deliquescent → c. Zinc chloride

3. **Understanding Hygroscopic:**
- Hygroscopic substances also absorb moisture but do not dissolve in it; they retain their solid state.
- **Example:** Cobalt chloride is hygroscopic as it absorbs moisture but does not turn into a solution.
- **Match:** C. Hygroscopic → a. Cobalt chloride

4. **Understanding Food Additive:**
- Food additives are substances used to preserve food or enhance its flavor.
- **Example:** Sodium chloride (table salt) is commonly used as a food additive for preservation and flavor enhancement.
- **Match:** D. Food additive → b. Sodium chloride

### Final Matches:
- A. Efflorescent → e. Washing soda
- B. Deliquescent → c. Zinc chloride
- C. Hygroscopic → a. Cobalt chloride
- D. Food additive → b. Sodium chloride

### Summary of Matches:
- A - e
- B - c
- C - a
- D - b