The correct answer is c. Jenna and Tyler do not know the chances of passing on cystic fibrosis to their future offspring.
Cystic fibrosis is a genetic disorder which can be inherited from the parents. This disease affects mostly lungs but can affects liver, pancreas and other organs of the body such as digestive system. Cystic fibrosis can occur in offspring when he and she inherit one copy copy of gene that causes cystic fibrosis from each parent. In this question Jenna knows that she may carry a gene that causes cystic fibrosis but Tyler seems to be a normal man who does not gene causing cystic fibrosis.