Which of the following is a tetrabasic acid?

Heating $(NH_4)_2Cr_2O_7$ produces a gas. This gas can also be obtained by:

Match the following List-$I$ (Acid) with List-$II$ (Reagents used for preparation):
| List-$I$ (Acid) | List-$II$ (Reagents used for preparation) |
| :--- | :--- |
| $A. H_3PO_2$ | $I. \text{Red } P_4 \text{alkali}$ |
| $B. H_4P_2O_5$ | $II. \text{White } P_4 \text{alkali}$ |
| $C. H_3PO_4$ | $III. PCl_3; H_3PO_3$ |
| $D. H_4P_2O_7$ | $IV. P_2O_5; H_2O$ |
| | $V. H_3PO_4; \Delta$ |

Which one of the following statements is not correct regarding phosphine?

Discuss the general characteristics of Group $15$ elements with reference to their electronic configuration,oxidation state,atomic size,ionisation enthalpy and electronegativity.

Which is the correct statement for the given acids?