The three characteristics that apply to an effective opening statement are:
1. **Debatable** - An effective opening statement should present a claim or perspective that can be challenged or supported, engaging the audience in a conversation or argument.
2. **States the writer’s opinion** - It should clearly express the writer's viewpoint or stance on the issue at hand, providing a clear direction for the argument or discussion.
3. **Logical** - The statement should be based on reasoning and evidence, laying a solid foundation for the arguments that will follow.
Including a call to action can also be effective, but it is not always essential for all opening statements. Avoiding controversy and stating only facts are generally not characteristics of effective opening statements as they might limit engagement and personal expression.