The oxidation number of an element in a compound is evaluated on the basis of certain rules. Which of the following rules is not correct in this respect ?
A. The oxidation number of hydrogen is always +1
B. The algebraic sum of all the oxidation numbers in a compound zero
C. An element in the free or the uncombined state bears oxidation number zero
D. In all its compouinds the oxidatiuon number of fluorine is -1
