This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitamins and Minerals, Subject name: Biochemistry
Which of the following tocopherol is the most active form of vitamin E? 
Select and explain. 
A. Alpha, B. Beta, C. Gamma, D. Delta
A: Alpha
Answer: A: Alpha 
Explanation: Vitamin E family contains tocopherols and tocotrienols. There are 4 vitamers a, b, g and d in each group. a-tocopherol is the most active form. Look at the isoprene side chain of tocopherol. All fat-soluble vitamins contain isoprene units. Structure of alpha tocopherol