"If Manfred is indeed the mysterious killer, then he is a dangerous psychopath. If he is a dangerous psychopath, then he should receive treatment in mental institution. From this it follows that if Manfred is indeed the mysterious killer, then he should receive treatment in mental institution" is
◦ modus ponens
◦ modus tollens
◦ contraposition
◦ disjunctive syllogism
◦ hypothetical syllogism