35. So little ________  about science that the lecture was my understanding.

Researchers have found clear and convincing evidence ________ happiness isthe key to better health and longer lives.

You can hardly imagine what great difficulty we had _________ the task.

“Well done, John.！ Not a single mistake _____ in your exam paper this time！”said the teacher.

There is no ________ thinking more about the matter. Take it easy.