The First Step in the Backcross Mating Strategy for QTL

The first step in the backcross mating strategy for QTL mapping is that

A) two inbred parental strains that differ in a quantitative trait are crossed to produce an F1.
B) the F1 offspring are crossed with each other.
C) the F2 offspring must contain chromosomes that are recombinant between the markers and the genes involved in the trait
D) each parent should contain the same alleles at each QTL.