For the carbocation (A) given in the reaction, first we can rearrange it by ring expansion (4 to 5) then we have two choices either H-shift or methyl-shift. My teacher told me that Hydrogen is the best migrator so according to me product (D) should form but in my textbook (C) is given as final product ?? Where am I wrong ? (or is my textbook wrong ?)
Also I have been taught that whenever there is a choice among H-shift, alkyl-shift or phenyl-shift we prefer H-shift since H is the best migrator. So why methyl-shift is happening here ? Please explain.
What's the concept I am missing ??