2. He delayed writing the book. He only started to write it until he had done a lot of research. * A. Only after he had done a lot of research did he begin to write the book. B. He did a lot of research after he finished writing the book. C. He delayed writing the book as he had already done any research. D. It was only when he had written the book that he did a lot of research. 3. The man left the key inside the locked house. He could not get into the house. * A. If the man did not lock the house, he could get into it. B. If the key was not inside the house, the man could get into it. C. Leaving the key inside the house, the man could get into the house. D. If the man had not left the key inside the house, he could have got into it. 4. Mary was trying to swim in the sea alone. She should never have been allowed to do so. * A. When Mary left to swim in the sea alone, she said she knew what she was doing. B. It would probably be wrong to let Mary swim in the sea on her own. C. No one could have stopped Mary from trying to swim in the sea by herself. D. Someone ought to have stopped Mary from attempting to swim in the sea on her own.