The boiling point of para nitrophenol is greater than that of ortho nitrophenol, because
A. there is intermolecular hydrogen bonding in para nitrophenol and intramolecular hydrogen bonding in ortho nitrophenol
B. there is intramolecular hydrogen bonding in para nitrophenol and intermolecular hydrogen bonding in ortho nitrophenol
C. both have the same kind of hydrogen bonding
D. para nitrophenol is polar, while ortho nitrophenol is non-polar