做“验证绿叶在光下合成淀粉”的实验时，要先将天竺葵放到黑暗处一昼夜的目的是（    ）

阅读短文，下列问题

    Many people go to school for an education. They learn languages, history, politics, geography, physics, chemistry and mathematics. Others go to school to learn a skill so that theycan make a living.

    School education is very important and useful. Yet, no one can learn everything from school. A teacher, no matter how much he knows, cannot teach his students everything they want to know. The teacher's job is to show his students how to learn. He teaches them how to read and how to think. So, much more is to be learned outside school by the students themselves.

    It is always more important to know how to study by oneself than to memorize some facts or a formula（公式）. It is actually quite easy to learn a certain fact in history or a formula in math. But it is very difficult to use a formula in working out a math problem.

Great scientists before us didn't get everything from school. Their teachers only showed them the way. Edison didn't even finish primary school. But they were all so successful. They invented so many things for mankind. The reason for their success is that they knew how to study. They read books that were not taught at school. They would ask many questions as they read. They did thousands of experiments. They worked hard all their lives, wasting not a single moment. Above all, they knew how to use their brain.

    My dad really likes gardening, so he built a 1in our yard. He plants a lot of 2 and this year we have onions, beans, cabbages, tomatoes, potatoes and carrots. Now, we are starting to grow fruits3 grapes, strawberries and pears.

    Growing plants isn't that easy. First, we have to 4 seeds(种子), which we buy at a store called “Garden Nursery”. Next, we turn the soil(土壤) over, and then 5the seeds. We then wait until the seeds come out from the soil and grow into little leaves. My father and I water them every day. We have to do this 6 vegetables are just like us—they need water, air and food, so they can grow better and more 7.

    Autumn is the season to 8. The garden gives us a lot of fresh vegetables and fruits to eat. We may 9 get some vegetables that we cannot get at the supermarket.

    With time and hard work, I have learned to take care of the plants in our garden. It is really a great 10.