In humans, being a tongue roller (R) is dominant to being a non-tongue roller (r). A man who is a tongue roller marries a woman who is also a tongue roller and who is homozygous for tongue rolling. The man's mother was a non-roller. What is the probability that their first child will be a non-roller? begin{tabular}{|l|} hline 100% hline 75% hline 50% hline 25% hline 0% end{tabular}.