[clairvoyant]

I'll have exam in organic chemistry soon, so I have one question (equation actually) that pops out in tests and gives me a headache cause I'm in dilemma what to do

It is a reaction between lactose and 4 moles of N-methylphenylhydrazine (C6H5-N(CH3)-NH2).

The problem is that I have two ways to think about it. In one hand, when aldohexose reacts with 3 moles of phenylhydrazine, we get an osazone of course. On the other hand, I have this part in my book where it sais that when aldopenthose reacts with N-methylphenylhydrazine it gives an alkazone, where every -OH (and aldehyd) group is substitued with =N-N(CH3)-H5C6. It also sais that aldohexoses give same reaction with N-methylphenylhydrazine (they give alkazones).

So, if I take that malthose gives an alkazone, and I have 5 -OH groups there that can react (the sixth, on C4, makes the bond with galactose and I suppose only glucose molcule will react), which one will not react with hydrazine? The last one? And if it gives osazone, then I have one mole too much...then I suppose, that mole would give one carbonyl group on the third C atom of the glucose. But I'm definetely not sure.  

I really hope someone understood me, cause I sound cunfusing even to myself Anyway, if anyone knows what is soulution, please help me. I'm going to study some more now