Final answer:
The correct choice is: 'When I looked into the rectangle, I saw a face looking back at me, but I didn't recognize it.'
Step-by-step explanation:
The correct choice that shows the same sentence properly written in past tense is:
O When I looked into the small rectangle, I saw a face looking back at me but I didn't recognize it.
This choice correctly uses the past tense to describe the action of looking into the small rectangle and seeing a face looking back. It also uses the past tense to indicate that the speaker did not recognize the face. The other choices either mix present and past tense or use incorrect past tense forms of the verbs.
Learn more about Past tense in English