pH of `0.1M Na_(2)HPO_(4)` and `0.2M NaH_(2)PO_(4)` are respectively: `(pK_(a)"for" H_(3)PO_(4)` are `2.12, 7.21` and `12.0` for respective dissociation to `HPO_(4)^(2-), HPO_(4)^(-)` and `PO_(4)^(3-))`:

Options

A. `4.7,9.6`
B. `9.6,4.7`
C. `9.3,4.4`
D. `4.4,9.3`

Explanation

To find the pH of `0.1M Na2HPO4` and `0.2M NaH2PO4`, we will use the given pKa values for the dissociation of phosphoric acid (H3PO4) and the properties of amphoteric compounds.

### Step-by-Step Solution:

1. **Identify the Relevant pKa Values**:
- For H3PO4, the pKa values are given as:
- pKa1 = 2.12 (for H3PO4 ↔ H2PO4⁻)
- pKa2 = 7.21 (for H2PO4⁻ ↔ HPO4²⁻)
...