Which of the following compounds will show a dipole moment?

Which of the following is non-polar?

Which of the following is non-polar?

Given below are two statements:
Statement-$I$: Since fluorine is more electronegative than nitrogen,the net dipole moment of $NF_3$ is greater than $NH_3$.
Statement-$II$: In $NH_3$,the orbital dipole due to lone pair and the dipole moment of $N-H$ bonds are in opposite direction,but in $NF_3$ the orbital dipole due to lone pair and dipole moments of $N-F$ bonds are in same direction.
In the light of the above statements,choose the most appropriate from the options given below.

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?

Determine the correct sequence of polarity for the following molecules:
$(1)$ Benzene
$(2)$ Inorganic Benzene $(B_3N_3H_6)$
$(3)$ $PCl_3F_2$
$(4)$ $PCl_2F_3$
(Where $P = \text{polar}$,$NP = \text{non-polar}$)