b
The molecule \(ML _{ x }\) is planar with \(7\) pairs of electrons around \(M\) in the valence shell.

There will be \(5\) bond pairs of electrons and two lone pairs of electrons. The electron geometry will be pentagonal bipyramidal and molecular geometry will be planar.

\(5\) Bond pairs of electrons will be in one plane and two lone pairs of electrons will be opposite to each other, one above the plane and other below the plane. This will minimize the electronic repulsion.

Hence, the value of \(x\) is \(5\)