题干

右图表示在一个有限环境中某一种群增长的曲线,下列有关叙述正确的是(   )

①K值是环境条件所允许达到的种群数量最大值
②在K值时,种群的增长率最大
③如果不考虑迁入迁出等其它因素,在K值时出生率大致等于死亡率
④假设这是鱼的种群,当种群达到K值时开始捕捞,可持续获得最高产量

A:①②

B:①④

C:①③

D:③④

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答案(点此获取答案解析)

C

同类题3

请用适当的词完成下面的短文, 补充所缺的单词。每个空只能填写一个形式正确,意义相符的单词。

    If you pay a visit to Liu Hasheng's restaurant in Harbin, you will find 18 robots there. They are ready to serve you and ____ sure that your dining experience is perfect. After the visit, you can tell others that robots serving customers isn't a dream any more.

    It's wonderful to see ____ the 18 robots work in the restaurant. The wonder starts when you walk in. You ‘ll see a robot come up and say, "Earth person, hello! ____ to the Robot Restaurant." When you have ordered your ____, the robots in the kitchen begin to do the cooking. After the food is ____, a robot waiter will glide(滑行) out of the kitchen to serve you with the meal you've ordered. And as customers enjoy their delicious food, a robot ____lovely songs for them.

    You may ask, "Where did all these robots come ____?" Liu said they were designed(设计) and ____ by the Harbin Haohai Robot Company. Liu said he invested(投资) 5 million yuan in the restaurant, with ____ robot costing 200,000 yuan to 300,000 yuan. And the whole robot team is managed by the workers in the computer room.

    After a busy day, all the robots will go for a "meal", which is electricity. After 5 hours, the robots can continue their work for a day. The restaurant now provides a menu ____ more than 30 dishes(菜肴), and the average(平均) cost for a dinner is about 40 to 50 yuan. Do you want to go and have a try in this restaurant?