Oil prices cannot drop unless Venezuela increases its production.
A.
It's not the case that oil prices will drop, and it's not the case that
B.
Venezuela will increase its production.
C.
If Venezuela increases its production, then oil prices will drop.
D.
Only if Venezuela increases its production will oil prices drop.
E.
Either Venezuela will not increase its production, or oil prices will not drop.
F.
If Venezuela does not increase production, then oil prices will drop.