It should be choice 1. We have two parents with an identical condicion (lactose persistent), let's say they are LL or Ll, thus they could form the following gametes: L or l, so the possible outcomes (genotypes) when their gametes combine are: LL, Ll, lL, ll. Assuming the lactose persisten trait is dominante, either, LL, Ll, lL will show lactose persistance, the only genotype that will display a different phenotype is, ll. So, lactose non-persistence is a recessive trait choice 1.