You don't need B at all.
Fill C from A leaving 4 liters in A.
Dump out the water in C.
Then fill C from A again, leaving 1 Liter in A
Depending on your interpretation, that could be seen as 3 pours: dumping the water from C requires pouring it out.
Wait a minute! Does that mean that if I use a siphon I can claim I did it with 0 pours?!?! I'm a genius!