A geneticist is studying a family with an autosomal dominant disease that has been mapped to chromosome 7. Two DNA markers, A and B, are located on chromosome 7 near the disease locus. The following LOD scores were obtained:

 θ = recombination frequency
                        LOD score
       Marker A       θ = 0.10     2.1
       Marker A       θ = 0.20     0.1
       Marker B       θ = 0.05     1.8
       Marker B       θ = 0.10     0.4

Based on the LOD scores, which marker is most closely linked to the disease locus?