题干

请根据以下装置,下列正确的是(  )

A:甲装置可以用来验证光合作用需要水

B:乙装置放在有光环境中,可以验证光合作用有氧气产生

C:丙装置可以用来验证呼吸作用需要水作为原料

D:丁装置设置合理,可以用来验证蒸腾作用

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答案(点此获取答案解析)

B

同类题2

阅读下列短文,从每题所给的四个选项(A、B、C和D)中,选出最佳选项。

B

    Our risk of cancer rises as we age. So it makes sense that the elderly should be routinely screened for new tumors(肿瘤)—or doesn't it?

    While such careful tracking of cancer is a good thing in general, researchers are increasingly questioning whether all of this testing is necessary for the elderly. With the percentage of people over age 65 expected to nearly double by 2050, it's important to consider the health benefits of screening and the costs of routine testing.

    In many cases, screening can lead to additional operations to remove cancer, which can cause side effects, while the cancers themselves may be slow-growing and may not cause serious health problems in patients' remaining years. But the message that everyone must screen for cancer has become so ingrained that when health care experts recommended that women under 50 and over 74 stop screening for breast cancer, it caused a strong reaction among doctors, patients and advocacy(拥护) groups.

    It's hard to uproot deeply held beliefs about cancer screening with scientific data. Certainly, there are people over age 75 who have had cancers detected by routine screening, and gained several extra years of life because of treatment. And clearly, people over age 75 who have other risk factors for cancer, such as a family history, should continue to get screened regularly. But for the remainder, the risk of cancer, while increased at the end of life, must be balanced with other factors like a remaining life expectancy.

    A recent study suggests that doctors start to make more right decisions about who will truly benefit from screening—especially considering the explosion of the elderly.

    It's not an easy guess to make, but one that makes sense for the whole patient. Dr. Otis Brawley said, "Many doctors are ordering these tests purely to protect themselves against medical disputes(纠纷). We need to think about the good use of health care and stop talking about the rationing(定量配给制) of health care."

    That means making some difficult decisions with elderly patients and going against the misguided belief that when it comes to health care, more is always better.

同类题5

阅读下文,完成下列各题。

孙子的麦收

王旭

       乌云从南面的天空急急地飞过来,眼看就到头顶上了,大老刘急忙抱起塑料布往麦场里跑,今天收的麦子,不能被雨水冲了。

       电话响了。谁的电话?真是添乱。哦,是儿子的,儿子大学毕业后,在城里工作,成了家,有了孩子。

      “爷……”

      “哎……是孙子哟。”大老刘心里灌了蜜,劳累顿时全散了。

      “我今天收麦了!”孙子高兴地喊。

       大老刘一听,恁小的孩子能收麦?上哪收麦?城里有麦子?收麦是很累人的活计,时间紧,天热,活计重,活计脏,一个麦收等于两个秋收,人们说“一麦两秋”就是说收麦活重。大太阳底下如火烤,麦秸上有一层厚厚的灰,手一动,灰便飞起来。还有小蠓虫子围着头飞来飞去,直打脸,往鼻子嘴里钻。

      “你﹣﹣收麦?累不累?”“一点也不累。好玩着呢!”

        好玩?收麦子好玩?割麦时要蹲在熟透的麦子边,蹲累了,跪地上,跪累了,坐地上,一点点地往前欠着身子,一把一镰才割四指远,一天也就割亩把地。一天下来,浑身是灰,往床上一躺,像散了架子。

      “今天我和爸妈一起去体验农家乐了,妈妈还给我买了一身运动装,我穿上可好看了。带上饮料,我最爱喝的。”

      “这不是旅游吗?”

      “差不多,你猜我割了多少麦子?”

       这一问难住大老刘了,孙子一天能割多少麦子呢?半亩不能,有一间房子大的一片儿就不少了。他想着。

      “猜不到吧。我割了二百六十棵麦子!”孙子很有成就感。

       天哪,孙子能用棵来统计割麦的数量!

      “割那么多,累吗?”大老刘算是明白了,孙子是玩,不是收麦子。

      “不累!妈妈一边给我打着伞,一边给我拿饮料,一会儿喂我一口,一会儿给我擦擦汗;爸爸接我割的麦子,我割一棵,爸爸计一棵,一共二百六十棵!”

       大老刘没有回话,只“噢”了一声。

      “爷,唐诗错了!就那句‘谁知盘中餐,粒粒皆辛苦’!”

      “咋错了?”大老刘心里一疼,像是被谁狠狠地砸了一下,赶紧问。

      “我觉得,收麦一点也不辛苦啊!我把麦棵交给加工人员,他给我打了二万零五十八粒麦子,可是哪有一点辛苦啊?所以‘粒粒皆辛苦’错了!”

       乌云遮蔽了天空,远处传来了雷声。

       大老刘愣了半天,才说:“明天你回来帮爷爷割麦子吧。”

       第二天,艳阳高照,真是麦收的好天气!大老刘只带了孙子一个人下了田。只一会儿工夫,孙子就脸色潮红,汗珠直滴,动作也慢了下来,开始用求救的眼光看向爷爷。大老刘什么话也没说。孙子越割越慢,终于割不动了。大老刘指着孙子割下的麦子说:“你数一数,今天你割了多少粒麦子?”孙子看着自己浑身湿透的衣服和那割下的一点点麦子,一下子呆住了……

       一进门,孙子就累得瘫倒在地上,苦着脸说:“真是‘粒粒皆辛苦’啊……”看着孩子疲劳的样子,爸爸妈妈噌的一下脸红了,大老刘却高兴地笑了。

(选自2016年第7期《微型小说选刊》,有删改)