Solution:
The sentences express wishes or regrets about the present or past. We use the past simple for wishes about the present and the past perfect for wishes about the past. 'If only' is similar to 'I wish'.
- I wish I were taller. (Using past subjunctive 'were' for wishes about the present state).
- I wish you would tell me more. (Expressing a wish for someone's future action or behavior).
- If only I had bought a more interesting book to read. (Expressing regret about a past action).
- I wish I didn't have this awful headache. (Using past simple for wishes about a present situation).
- If only I could go to sleep. (Expressing a wish for an ability or possibility).
- I wish you would not knock before you come into my room! (Expressing annoyance about someone's present or future action).
Answer: were, would tell, had bought, didn't have, could go, would not knock