问题详情：
Everyone has seen plants growing, but have you ever thought 61. they get their food? In the seventeenth century, 62 European scientist called Van Helmot asked this question. Like most people, he thought plants get their food from soil. However, he decided to test the theory with 63 (experiment).
First, he dried some soil, put it into a pot and weighed it. Next, he weighed a small tree, planted in in the pot and added rain water. Then, he watered it 64 (regular) with rain water.
After five years, he removed the tree from the pot and weighed it again. He found that the tree had gained a huge amount of weight. When he weighed the soil, 65 , it was almost exactly the same as it had been five years ago . So he drew the conclusion that the tree grew by drinking water. Though it turned 66 to be wrong, he showed the importance of the use of 67 (science) evidence to support ideas.
We now know that plants and trees make their 68 food. Their leaves, when 69 (expose) to the air and sun, are like factories which can change the energy from the sun into chemical energy. During this process, oxygen and sugar 70 (produce). The oxygen is released back into the air, and the sugar is used by the plant as food.
【回答】
61．how 62. a 63. experiments 64. regularly 65. however
66. out 67. scientific 68. own 69. exposed produced
知识点：语法填空
题型：未分类
