Great question. There are some diagrammable statements in this stimulus, so it wouldn't hurt to make a few diagrams if you're having trouble seeing what inference you can push out.
The first diagrammable statement is that if we don't distribute wealth, then we'll have intolerable economic inequalities.
From this, we know that if we don't distribute wealth, then we'll have violence. The contrapositive of this chain is that if we don't have violence, then we must distribute wealth
don't have violence - >don't have intolerable economic inequalities - >must distribute wealth
The politician ends the argument by telling us that we must do whatever is necessary to stop the violence. The contrapositive of our chain tells us that redistributing wealth is necessary to stop violence, so we know the politician believes that we must redistribute wealth.
(B) says, "It is our nation's responsibility to redistribute wealth."
This is the inference we can push out by combining the statements in the stimulus and is the implication of the argument that the politician presents, so it must be true. Thus, (B) is the correct answer choice.
Does this make sense? Let us know if you have any other questions!