题干

如图为某种兰花,其花矩细长,顶端贮存着花蜜,它的传粉需借助具有细长口器的蛾在吸食花蜜的过程中完成,下列叙述正确的是(    )

A:蛾口器的特征决定兰花花矩变异的方向

B:口器与花矩的相互适应是共同进化的结果

C:花矩变长是该兰花新种形成的必要条件

D:蛾的口器会因吸食花蜜而变得越来越长

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答案(点此获取答案解析)

B

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   Almost every day, we discuss the topic of health, especially for kids. But what is health? “Health” means eating well, getting enough exercise, and having a healthy weight. Let’s read the following rules. They can help you stay healthy.
   1. Eat a variety of food, especially fruit and vegetables. We all know that eating fruit and vegetables can help us stay healthy, but many of us only eat our favorite food. Remember that we can only get the nutrition (营养) we need by eating different kinds of food, especially fruit and vegetables.
   2. Drink water and milk most often. Everyone knows that water is important. Besides that, kids need plenty of calcium (钙) to grow strong bones, and milk is rich in it. Every day, you should drink at least three cups of milk, when you are 9 years old or older. You should also try to have less sugary drinks, like soda and coca. They include a lot of sugar. Sugar only includes calories (热量), not important nutrition.
   3. Listen to your body. When you are eating, notice how your body feels. When your stomach feels comfortably full, stop eating. Eating too much makes you feel uncomfortable. If you do it too often, it can make you unhealthy and fat.
   4. Limit screen time. What's screen time? It's the amount of time you spend watching TV, movies and playing computer games. The more time you spend on these sitting-down activities, the less time you spend playing sports, like basketball, and doing other activities like riding and swimming. Try to spend no more than 2 hours a day on screen time.