Which of the following compounds is non-polar?

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?

For which of the following molecules is the dipole moment $\mu \ne 0$?

Which set contains molecules with $\mu = 0$?

Which of the following molecules has the maximum value of dipole moment?

Which of the following compounds exhibits a net dipole moment?