Tetra basic acid H4P2O7:

H4P2O7 is a tetra basic acid, which means it can donate up to four hydrogen ions (H+) in an aqueous solution. This acid is commonly known as pyrophosphoric acid.

P=O bonds in H4P2O7:

The formula H4P2O7 indicates that there are two phosphate groups (P2O7) in the molecule. Each phosphate group contains one central phosphorus atom (P) bonded to four oxygen atoms (O). Therefore, to determine the number of P=O bonds in H4P2O7, we need to count the number of oxygen atoms bonded to the phosphorus atoms.

Structure of H4P2O7:

The structure of H4P2O7 can be represented as follows:
H H H H
\ / \ /
O=P--O--P=O
/ \ / \
H H H H

In this structure, each phosphorus atom is bonded to three oxygen atoms through single bonds (P-O). However, one oxygen atom in each phosphate group is also bonded to the other phosphorus atom through a double bond (P=O), forming a pyrophosphate linkage.

Therefore, each phosphate group contributes one P=O bond to the overall structure of H4P2O7. Since there are two phosphate groups in H4P2O7, the total number of P=O bonds in the molecule is two.

Conclusion:

The correct answer is option 'B', which states that there are two P=O bonds present in the tetra basic acid H4P2O7.