11. You’d better do that again.

54. Various substances differ widely in their magnetic(磁性的)characteristics.

23. I'm thinking about a visit to Paris.

63. He has taught English in this university ever since he moved to this city.

68. It’s very important to maintain your current weight through exercise and healthy eating.

67. You needn’t go there anymore. He already knows about it.

69. It normally takes a semester for a college freshman to adjust to his college life.

66. If you decided to learn a new language, you would have to devote all your efforts to it.

57. In an age of plenty, we feel spiritually hungry.

32. Do you think you can do it by yourself?