 Whenever \(A \land \neg D\) is actual, so is \(C\)—for no effect occurs without any of its causes. Furthermore, whenever \(C\) occurs, so does \(B\). Hence, \(A \land \neg D\) is minimally sufficient for \(C\), and thus for \(B\). And \(A \land \neg D\) is a minimally sufficient cluster in a necessary condition for \(B\):