If we are solving an enthymeme with a missing conclusion, and one premise is an O proposition, then the conclusion:

A) can be any proposition
B) can only be an I or O proposition
C) can only be an E or O proposition
D) can only be an O proposition
E) can only be an E proposition

O Proposition

In traditional logic, a proposition that states that some members of a category do not share a specific attribute.

Enthymeme

An enthymeme is a rhetorical syllogism commonly used in persuasive speech, where one of the premises is not explicitly stated but is implied, making the argument rely on the audience's recognition of the unstated premise.

Conclusion

The final part of something, typically a process or discussion, where the main points or decisions are summarized or determined.