You might not be able to use a dictionary in the following situations:
- On an airplane - If electronic devices are not allowed or the use of physical books is restricted during certain phases of flight.
- Taking a test - Many standardized tests or classroom assessments prohibit the use of dictionaries or other reference materials to ensure the integrity of the test.
- In a park - While using a dictionary in a park is generally feasible, it could be impractical if you don't have one readily available or if you don't want to carry the extra weight.
Given these considerations, the best answer would be "All of the choices," as you might encounter restrictions or impracticalities in all of those situations.