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如图所示是两种细胞的亚显微结构示意图,请据图判断下列有关说法正确的是(    )

A:用含18O标记的丙氨酸的培养液体外培养图一所  示细胞,该细胞内合成抗体的过程中,脱水缩合产生了H218O,则其中的18O来自于该丙氨酸的羧基或R基

B:图一所示细胞合成的抗体以主动运输方式进入内环境,需要该图中⑥提供能量

C:以18O标记的H218O分别研究图二所示细胞的有氧呼吸和光合作用过程,发现有氧呼吸和光合作用产物中最先出现的放射性物质分别是CO2和O2

D:若将图一,图二所示细胞同时置于质量分数为30%的蔗糖溶液中都可以观察到质壁分离现象

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C

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    For some students, getting better grades can seem like an impossible task sometimes. With the challenges(挑战) of school, just paying attention in class or studying hard isn't always enough. But what if there were other ways for students to improve their grades? For parents and students who have ever wondered if this is possible, now you can rest easy. Research suggests that a person who likes doing activities can improve their grades.

    Scientists think that those students who are active are not just exercising their bodies, but also exercising their brains(大脑). In turn, they can be able to improve their grades at school.

    In the most recent study, researchers found that when children played for half an hour each day, they were better at organizing(组织) their schoolwork as well as doing project work and learning traditionally “difficult” subjects, such as maths.

    What does this mean for children who aren't active? Researchers think that if kids don't get enough activities, they are going to be at a disadvantage when it comes to school performance.

    In the research experiment, a group of children skipped with ropes(跳绳), played basketball and did a number of other games or exercises. Another group of children didn't do any activities. They took part in testing both before experiment and after the experiment. Testing was mainly for maths and reading skills. Results showed that the children in the activity group did better on the tests than those who had no activity.

    All work and no play will not only make Jack a dull(迟钝的) boy, but will also negatively(消极地) affect his grades in school, according to a new study published in the Journal of Pediatrics.

    Parents complain(抱怨) children today are actually less active and they always worry about their grades. Dr. Belton, an expert, said, “If you'd like to see your kids do better in school, have them close their books, set down their pencils and go outside to play.”