Highest oxidation state of Mn is exhibited in $\mathrm{Mn_2O_7}$. The correct statements about $\mathrm{Mn_2O_7}$ are

(A) Mn is tetrahedrally surrounded by oxygen atoms.

(B) Mn is octahedrally surrounded by oxygen atoms.

(C) Contains Mn-O-Mn bridge.

(D) Contains Mn-Mn bond.

Choose the correct answer from the options given below :