What about always being able to select an option, no matter whether you meet the requirement or not? There are certain advantages:
- you take no chances of a bug preventing the reader from making a choice (when he or she met the requirement)
- you allow the reader to cheat (which is what many like to do)
- it reminds of the times when gamebooks were hard copy
This is the approach I used for the Android version of The Path of Light.