Under International Law,what Is the Difference Between a Treaty and a Convention

Under international law,what is the difference between a treaty and a convention?

A) A treaty is an agreement,and a convention is typically the meeting at which the treaty was drafted.
B) The two terms have the same meaning,thus there is no difference between them.
C) A treaty is an agreement negotiated directly be the signatory nations,whereas a convention is first drafted by a sponsoring international organization,after which,nations can decided whether to be bound by it.
D) Conventions usually have only a few signatory nations whereas treaties usually have many.