(A) Pact
(B) Alliance
(C) ** Non-Aggression Pact
(D) Axis Alliance
EXPLANATIONS BELOW
Concept note-1: -Contents. The Molotov-Ribbentrop Pact was a non-aggression pact signed in 1939 by Nazi Germany and the Soviet Union shortly before World War II. In the pact, the two former enemies agreed to take no military action against each other for the next 10 years.
Concept note-2: -A non-aggression pact or neutrality pact is a treaty between two or more states/countries that includes a promise by the signatories not to engage in military action against each other. Such treaties may be described by other names, such as a treaty of friendship or non-belligerency, etc.
Concept note-3: -German-Soviet Nonaggression Pact.
Concept note-4: -Non Agression just means neither of the two countries will declare on each other by themselves. But a guarantee will still trigger, they are bound to defend the guaranteed country, regardless of other treaties with you.