1.
(1) d.
(2) a.
(3) d.
2.
(1) I [<could have won> the race if I <had not fallen>]. <仮定法過去完了>
(2) If one [<were to> hear him speak Korean], one would take him for a Korean.
※仮定法未来:if S were to ~ もし仮にSが~すれば hear(知覚動詞) O ~(動詞の原形) Oが~するのを聞く
(3) [<Had I known> he was not] feeling well, I <would never have asked> him to come. <仮定法過去完了>
※Had I known(倒置):ifを使わない仮定法過去完了
3.
(1) a. did → had done(過去完了形) ← 仮定法過去完了:過去の事実の反対を仮定
(2) c. can → could(過去形) ← 仮定法過去:現在の事実の反対を仮定
4.
(1) Were I you, I would accept her offer. <仮定法過去> = If I were you, I would accept her offer.
(2) If only I had told him the truth yesterday. <仮定法過去完了>
※if only S had ~ed(過去完了形) 過去にSが~してさえおけば良かったのになあ <後悔の念を表す表現>
参考にしてください。