How can you tell if a molecule has a dipole moment?

How do you know if a molecule has a dipole moment?

The larger the difference in electronegativity between the two atoms, the more electronegative that bond is. To be considered a polar bond, the difference in electronegativity must be large. The dipole moment points in the direction of the vector quantity of each of the bond electronegativities added together

c (diamond),

sio2 (quartz)

im doing test rn im going with 2 but ill give answer if itss wrong,   : )