Answer:
Autosomal dominant
Step-by-step explanation:
As given here that;
A trait appears equally in both males and female, and offspring can inherit the trait both from father and mother, it indicates that this trait is not sex limited or sex linked.
And its also given that all effected individuals have at least one affected parent.
So lets parents as
A*a and A*a
so offspring are AA, Aa, Aa and aa.
If it is dominant trait, 3 out of 4 offspring are affected.
If it is recessive then 1 out of 4 offspring is affected, but here both the parents are unaffected, so it is autosomal dominant trait.
example 2; cross between aa× Aa
offspring : Aa, Aa, aa, aa
3. AA× aa
Aa, Aa...
4. AA× Aa.
AA ,Aa, AA, Aa