Final answer:
For accurately testing vitamin A levels, protecting the specimen from light is essential since vitamin A is light-sensitive and its degradation could lead to faulty results.
Step-by-step explanation:
When collecting a specimen for vitamin A testing, special precautions need to be taken to ensure the accuracy of the results. One such precaution is to protect the sample from light, as vitamin A is light-sensitive and can degrade upon exposure to light, which would potentially lead to inaccurate measurements. Therefore, the correct answer is (a) Protect from light. It is not typically necessary to freeze the sample immediately or use a red-top tube specifically, and while contact with air is generally to be minimized in all types of specimen handling, it is light exposure that is the primary concern for vitamin A samples.