Which statements regarding the enforcement of international law are correct?

A、Statesmaychoosevariousmethodstoenjoytheirrightsandenforcetheirobligations.
B、Thereisnouniformlawenforcementmachinery.
C、Statesmaytakeself-helpmeasuresthroughdiplomaticmeans.
D、Statesmayuseforceinself-defense.