Final answer:
If the disease can be inherited from the father to sons in a pedigree, it indicates that the disease is X-linked recessive.
Step-by-step explanation:
If you were looking at a pedigree and noticed that a particular disease COULD be inherited from father to sons, you can conclude that the disease is X-linked recessive. In X-linked recessive inheritance, males either have the disease or are genotypically normal, while females can be genotypically normal, a carrier, or affected with the disease. The disease is passed from an affected father to his daughters, who are carriers, and to his sons, who are affected.