Initially I was pretty sure that the correct answer had to be "None of them", since global variables are stored in the data memory, but then I've found this book from Robert Lafore, called "Object Oriented Programming in C++" and it clearly states that, according to the C++ standard, global variables are stored on the heap. Now I'm pretty confused and can't really figure out what's the correct answer to the question that has been asked.
Why would global variables be stored on the heap? What am I missing?
EDIT: Link to the book - page 231