I guess you forgot to add the picture or so.
Based on the Complementarity of the 4 nucleotides, The thymine must always be placed in front of the Adenine, and the Cytosine must always be placed in front of the Guanine.
Any change in this rule causes the deformation of the DNA, and can sometimes cause fatal diseases like the melanoma (skin cancer) etc...
Hope this Helps! :)
Number 10 is A and Number 11 is B
