题目

如右图表示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．③④19．Easy ways to get healthy    I always hate the first few weeks of the new year，mostly because I-m sick to death of people in commercials who are all．"Let's diet!It's a new year!"You can always choose to switch it up!（36）EHere are some simple ways to get your healthy on all year around．Switch out bad habits for good ones．（37）GDo something as simple as swapping nighttime cookies for nighttime vitamins．    Catch some sleep．One of the most important things we can do for our minds and bodies is to make sure．we're getting enough sleep on a regular schedule．（38）F     Feed your mind．Keep your mind flexible and smart．Do crosswords，sudoku（数独）．Start a new hobby，read a book about something you don't understand-anything that challenges you to think differently and exercise that brain of yours．    （39）AI'm not suggesting you take on a brand new fitness quest，but take the stairs，park farther away，and find a hobby you enjoy that allows you to be active．Get organized．I'm not saying a whole repair of your entire world； start small．Organize a kitchen  cabinet．Purge （清除 ）yourself of stuff you  don't need．     Get rid of the mess．That means your mind is included too!Make lists．Get a calendar and mark down important days．Clear your mind and your home．（40）C     Smile．Overlook some of the bad things that are going on in your life．and focus on the good．There are positives in nearly every situation，even if it doesn't feel like it．Staying positive can help in nearly every aspect of your life!A．Change your activity up．B．Try exercising your brain too．C．You'll find it improves your mood．D．You are the one to improve yourself．E．lt's time to take charge of your health!F．Sounds boring，I know，but trust me---sleep is amazing for you．C．Start small，and don't plan to change your entire life in a week．