Select the most appropriate option to fill in the blank and complete the collocation.

Although she didn't reveal her plans clearly, I had a _______ idea.

rough

The most appropriate option to fill in the blank and complete the collocation is rough.

The sentence is about someone who has a general idea of what someone else is planning, even though the plans have not been fully revealed. The word "rough" means not detailed or precise. It is the most appropriate option because it conveys the idea that the person has a general idea of what the plans are, but they are not sure of all the details.

The other options are incorrect.

• Clear means easy to understand. It does not make sense to say that the person had a clear idea of the plans if they were not revealed clearly.
• Concise means brief and to the point. It does not make sense to say that the person had a concise idea of the plans if they were not revealed clearly.
• Complete means having all the necessary parts or elements. It does not make sense to say that the person had a complete idea of the plans if they were not revealed completely.