SELF DOUBT TIFR QUESTION

Question

https://gateoverflow.in/95703/tifr2017-b-8

IN THE SOLUTION      Now, consider n=1. The only Gray code possible is {0,1}. Hence no of Gray code == odd for n=1. 

                                     THE DOUBT IS THAT WHY NOT {1,0}  HENCE TOTAL 2 GRAY CODES FOR N=1???

Comments

Official answer by TIFR is A

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IT MEANS {1,0} AND {0,1} ARE TWO POSSIBILITES .... HENCE EVEN AND SELECTED ANSWER IS WRONG?