The given question is incomplete as the genotype of the parents is not given, so the answer is providing in the followings case:
1. dominant parent and recessive parent
2. heterozygous parents
Answer:
1. dominant parent and recessive parent:
dominant parents can be represented by LL and recessive parent is represented by ll, so the gametes would be L, L and l, l.
so,
L L
l Ll Ll
l Ll Ll
so there are all offspring in heterozygous condition as we known one or two dominant allele masks the recessive allele for the trait so 100% offspring can fold their tongue.
2. heterozygous parents
In this case, parents have Ll genotype and gametes would be L and l for each parent so,
L l
L LL Ll
l Ll ll
In this case, one is pure dominant and two heterozygous whereas only one is recessive so, the phenotype of offspring that cant fol the tongue would be:
3/4 = 75%