Question

Fill in the blank with an appropriate option:

I had forgotten to bring my camera so I _______ take any photographs.

• A. can't
  
• B. won't
• C. mustn't
• D. couldn't

Answer 1

The correct option is D couldn't

'Can't' indicates present impossibility.
'Won't' indicates a future impossibility.
'Mustn't' indicates prohibition.
'Couldn't' indicates inability in the past.
Here, past inability to take photographs is expressed. Therefore, the correct option is D: couldn't.