Which of the following pair of ions makes the water hard(temporary) ?

Explanation

To determine which pair of ions makes water hard (specifically temporary hardness), we can follow these steps:

### Step 1: Understand the Types of Water Hardness
Water hardness is classified into two types: temporary hardness and permanent hardness.

**Temporary hardness** can be removed by boiling water, while **permanent hardness** cannot be removed by boiling.

### Step 2: Identify the Ions Responsible for Temporary Hardness
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