In the addition of bromine to trans-anethole the reason more anti rather than syn addition product is formed is that.
a) There is probably some satiric hinderance taking place between substituents attached to the double bonded carbons.
b) No stable carbocation intermediate is formed while syn addition takes place
c) Anti addition takes place first as well as trans-anethole left over the reacts by syn addition
d) Isotopic variations of the chlorine atoms shifts the ratio in favor of anti addition