Element A burns in nitrogen to give an ionic compound B. Compound B reacts with water to give C and D. A solution to C becomes milky on bubbling carbon dioxide. Identify A, B, C and D.

Explanation

To solve the problem step by step, we need to identify the elements and compounds involved based on the given reactions and properties.

### Step 1: Identify Element A
The question states that element A burns in nitrogen to give an ionic compound B. Since we are looking for an element that can form an ionic compound with nitrogen, we can consider alkali or alkaline earth metals.

**Hint:** Think about which elements react with nitrogen to form stable ionic compounds.

### Step 2: Determine Compound B
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