Statement I: CCl₄ & CHCl₃ have zero dipole moment.
Statement II : All tetrahedral molecules have zero dipole moment.

CCl₄ has regular tetrahedral geometry.It is a symmetry molecule, dipole moment is zero.
 

μ = 0
But CHCl₃ dipole moment is not equal to zero
I is false
All tetrahedral  molecules have zero dipole moment need not be true always