according to the pedigree chart, which statement must be true?

Explanation:

As per the pedigree chart, only the males are shown as affected by the disease. Thus, it must be a sex-chromosomal inheritance, expressed in the Y chromosome or the male chromosome.  

As the females in the family are unaffected, hence the mother in the original parental generation cannot be a carrier.

It is likely that the father from the original parental generation might be the carrier.

As there are affected individuals in both the generation after the original parental generation ( the last generation having two more affected males), the statement that the chances of inheriting the decease with each successive generation is not true.

1. is geographic distribution

2 is increasing complexity

3 is transitional forms