Which of the following bonds is the most polar?

Identify the correct set of molecules with zero dipole moment.

Which of the following is the correct order of dipole moment for the given molecules?

Which of the following has the highest dipole moment?

Elements $X, Y$ and $Z$ have $4, 5$ and $7$ valence electrons respectively.
$(a)$ Write the molecular formula of the compounds formed by these elements individually with hydrogen.
$(b)$ Which of these compounds will have the highest dipole moment?

Pick out the molecule which has zero dipole moment.