Answer: D) Did he realize.
Explanation for this question is being written.
Answer: A) Only after posting the letter did I remember that I had forgotten to put on a stamp.
Answer: A) None but God can save us from this pandemic.
Answer: C) Only then did I understand why the tragedy had happened.
Answer: C) Only
Answer: B) Did her friend forgive.
Answer: B) Have I seen.
Answer: C) Did