在如图所示的透镜中，属于凸透镜的是______，它们的共同特点是______；属于凹透镜的是______，它们的共同特点是______．
根据中间厚边缘薄的透镜叫凸透镜，所以属于凸透镜的是ABD，共同特点是中间厚、边缘薄（或对光有会聚作用）；根据中间薄边缘厚的透镜叫凹透镜，所以属于凹透镜的是CE，共同特点是中间薄、边缘厚（或对光有发散作用）．
故答案为：ABD；中间厚、边缘薄（或对光有会聚作用）；CE；中间薄、边缘厚（或对光有发散作用）．
| 完形填空。 | ||||
| One of David's friends loved money very much, and 1 gave anything to anybody. Soon he became 2 . One day, he was 3 near the river with his friends when he slipped (滑倒) and fell in. His friends ran to help him. And one of them held out his hand and said, " 4 me your hand, and I will pull (拉) you out." The rich man's head went under the water and then came up again, 5 he didn't give his hand. Again another of his friends tried but again the 6 thing happened. Then David said, " 7 my hand, and I will pull you out!" The rich man took his hand and David pulled him 8 of the water. "You don't know our friend very well," he said to the 9 . "When you say 'give' to him, he does 10 , but when you say 'take', he takes at once." | ||||
|