Which of the following molecules has a zero dipole moment?

Which of the following is a polar compound?

Which of the following statements regarding $NH_3$ and $NF_3$ is correct?

Amongst $BeF_{2}$,$BF_{3}$,$H_{2}O$,$NH_{3}$,$CCl_{4}$ and $HCl$,the number of molecules with non-zero net dipole moment is ...... .

Which one of the following molecules is polar?

If the dipole moment of $HI$ is $0.38 \, D$ and the bond length is $1.61 \, \mathring{A}$,what is the percentage ionic character of the $H^{\delta +} - I^{\delta -}$ covalent bond (in $\%$)?