The teenager with a fiberglass cast asks the nurse if it will be okay to allow his friends to autograph his cast. Which response would be best? A. "It will be alright for your friends to autograph the cast." B. "Because the cast is made of plaster, autographing can weaken the cast." C. "If they don't use chalk to autograph, it is okay." D. "Autographing or writing on the cast in any form will harm the cast."

A: "It will be alright for your friends to autograph the cast." This response is quite positive and vague, which means it doesn't address any potential issues or concerns. It should not be discarded but compared to the other options for a more comprehensive answer. B: "Because the cast is made of plaster, autographing can weaken the cast." This response is incorrect, as it is mentioning that the cast is made of plaster, whereas the question states it's made of fiberglass. C: "If they don't use chalk to autograph, it is okay." This answer implies a condition for autographing that it is okay if his friends do not use chalk. This may be a good response as it only restricts the use of specific material. D: "Autographing or writing on the cast in any form will harm the cast." This answer is quite negative and implies that autographing in any form will harm the cast. It seems to be overly cautious and does not provide any useful information or reasoning behind the claim.

Given the analysis of each response, we can eliminate response B as it's factually incorrect. Response D appears to be excessively cautious and without sufficient reasoning. Response A is quite vague and could potentially be the correct answer. However, response C provides more specific and useful information by restricting the use of a certain material while permitting the autographing.

Based on the analysis of each response and their relevance to the question, the best response for the nurse to give is: C. "If they don't use chalk to autograph, it is okay."