Final answer:
The percent possibility of this couple's child having sickle cell trait is 50%.
Step-by-step explanation:
In order to determine the percent possibility of a couple's child having sickle cell trait, we need to consider the inheritance pattern of the trait. Sickle cell trait is inherited in an autosomal recessive manner. This means that both parents need to be carriers of the trait in order for their child to have the trait. If one parent is a carrier and the other is not, their child will not have the trait.
Given this information, we can determine that in this case, the couple has a 50% chance of having a child with sickle cell trait.
Therefore, the correct answer is option 3) 50.