In monohybrid cross, Right-handed parent is dominant over left-handed. A child with left-handedness probably can have the following genotypes of parents:
RR x Rr
Rr x Rr
rr x Rr
RR x rr
As we have discussed in Law of Segregation -
In this case, in order to have a left handed child from two right-handed parents, probable genotype of parents should be 'Rr x Rr'.
Hence, the correct option is (b).