Final answer:
Marc would use option A - creating a list on his hand and pointing to each finger - to indicate multiple toys in American Sign Language when asking his nephew which toy he wants for his birthday. So, the correct answer is option a.
Step-by-step explanation:
If Marc wants to ask his nephew, "Which one of these toys do you want for your birthday?" and needs to sign the word in bold, he would use the signing action described as creating a list on his hand and pointing to each finger, which corresponds to option A.
This action in American Sign Language (ASL) indicates that he is listing multiple options for the nephew to choose from. Since he is referring to multiple toys, he can't just point to one toy or use a singular indication. In ASL, listing is a common way to present options or choices within a question or a statement.