从物质循环的观点来看，动物体中碳元素究其来源是[]A．蛋白质中含有的碳B．糖类中含有的碳C．大气中的二氧化碳D．非生物碳酸盐中的碳-八年级生物

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• You _______ walk across the road. It’s dangerous.[ ]A. may notB. don’t have toC. must notD. needn’t-
• —_____ I open the window, Mum? —No, you _____. It's cold outside.[ ]A. Can, may not B. Can, mus
• To make our city more beautiful, rubbish ________ into the river. [ ]A. needn't be thrown B. mu
• 在“草→昆虫→青蛙→蛇→鹰”这条食物链中，含能量最多的是[]A．草B．青蛙C．蛇D．鹰-八年级生物
• You ______ do it even if you don't want to.[ ]A.can't B. mustn'tC.have toD.needn'
• -Must I park my car behind the building?-No, you _______. You _______ park it there.[ ]A.mustn'
• I'm sorry I ________visit next week.[ ]A. can't B. don't C. mustn'tD. won't
• 一个山丘长满马尾松、灌木、草本植物，树上有松鼠、松毛虫、捕虫的山雀、鹰，树下有苔藓、地衣、真菌等．据此回答下列问题：（1）上述环境及所有生物共同构成一个生态系统，从其-生物
• 在自然界的物质循环中，能把动植物遗体分解成二氧化碳、水和无机盐的一类生物是______．-生物
• 下面是某生物小组的“探究生态系统中动植物的数量关系”研究性课题的有关实验过程，请分析并回答问题．实验用具及材料：小虾、蚂蝗、水草、洗净的沙子、池水、有盖玻璃瓶．说明：4-生物
• Another popular idea is that the Stonehenge_ a kind of calendar. [ ]A. must be B. can't beC. mi
• Tony said that Lily _____ the pages of your diary.[ ]A. numberB. are numbering C. should number D. n
• Jeff can't come to the party, because he'll _______ help his mom. [ ]A. mustB. has to C. h
• —Can you give me a hand, Robin?—But, Helen, you ____ my help every five minutes. I ___ TV now.[ ]A.
• 腐生性微生物能将复杂的有机物分解成简单的______，供绿色植物再利用，因此，他们是生态系统中的______．-生物
• 有毒物质会沿着食物链和食物网流动、传递。[]-七年级生物
• Everyone _____ a good habit from an early age.[ ]A. startB. is startingC. are startingD. should star
• 生态系统中的能量最终来自[]A．植物体B．微生物C．动物体D．太阳能-八年级生物
• —This winter H1Nl has become very popular in our country. —Don't worry, itby our government.[ ]
• 羊吃草可以得到这些草所固定的太阳能总量的[]A．全部B．一半C．大部分D．小部分-八年级生物
• —Can you give me a hand, Robin?—But, Helen, you_____ my help every five minutes. I______ TV now.[ ]A
• — What can you do?— I_____ play football.[ ]A. canB. shouldC. may D. would-七年级英语
• -__________ you play tennis?-No. But I am good at playing football.[ ]A. CanB. MayC. MustD. Should-九
• —_________ I answer your question in Chinese? —No, you mustn't.[ ]A. MayB. CanC. MustD. Do-九年级英
• 下图为生态系统碳循环示意图，请据图回答下列问题。（1）由图可知，碳在生态系统中主要以_________的形式进行循环。（2）大气中的二氧化碳首先依赖于图中②所代表的_________进入-八年级生物
• 肉类和鸡蛋的价格比粮食和蔬菜高，从生态学的观点看，这是由于[]A．饲养动物麻烦，时间长，投资大B．动物性食品营养价值高C．食物链延长，能量流失多，动物性食品成本高D．栽培植-八年级生物
• —Jack.All the young trees____at once. —OK.I'll do it at once.[ ]A. must be watered B. must wate
• —I like the party so much, but I_ go home.It's too late.—What a pity! [ ]A. have to B. mustn�
• 能量流动和物质循环是生态系统的两个密切相关、不可分割的过程。[]-八年级生物
• I __________ dance but I___________ dance well.[ ]A. can; canB. can; can'tC. can't; canD.
• 下图是自然界碳循环的简图，图中甲、乙、丙各代表[]A．生产者、分解者、消费者B．消费者、分解者、生产者C．分解者、生产者、消费者D．生产者、消费者、分解者-八年级生物
• If I went to the moon,I _____ bring something unusual back to school.[ ]A.willB. canC. wouldD. shall
• 在“草→昆虫→食虫鸟→鹰”这条食物链中，全部昆虫消耗的能量比全部狼所消耗的能量[]A．多B．少C．相等D．大约相等-八年级生物
• —Could I use your pen? —Of course, you _______.[ ]A. must B. may C. can -九年级英语
• 在生态系统的碳循环中，二氧化碳进入生物体内是通过[]A．呼吸作用B．光合作用C．蒸腾作用D．扩散作用-八年级生物
• —Let's go to the movies tonight.—Sorry.I__ . I have to help my mother wash clothes.[ ]A. mustn&
• —Where's my watch? I can't find it anywhere.—It _ _ in your bag or under these books.[ ]A.
• 古书《说苑．正谏》中有这样一段记载：“园中有树，其上有蝉，蝉高居悲呜，饮露，不知螳螂在其后也；螳螂委身曲附欲取蝉，而不知黄雀在其傍也；……”这是比喻社会现象的寓言，但却反-八年级生物
• —He is tired now.He_____ stay at home and have a rest.—Thanks, doctor.[ ]A. has toB. maysC. needD. c
• —Could I borrow your dictionary?—Of course I _____.[ ]A. canB. mustC. shouldD. have to-八年级英语
• Henny _________be at home now because he phoned me from the school just now .[ ]A.mustn't B.isn
• 在生态系统中，能量流动的起点是[]A．从生产者固定太阳能开始B．阳光照射到绿色动植物体上时C．生产者被动物所食时D．分解者分解动植物遗体时-八年级生物
• Return home quickly. Your parents _____ be worried about you now.[ ]A. canB. may C. must D. could-九年
• 下图是有关生态系统中碳循环的示意图，请分析回答下列问题。（1）写出①②③④的生理过程及⑤产生C02的方式：①_________、②_________、③_________、④_________、⑤__
• 小华同学说：“爷爷讲在他小时候，村边的小河里有许多鱼、虾，稻田中有不少黄鳝和泥鳅。现在河里和稻田中几乎没有鱼、虾了。”这是什么原因呢？（1）请对上述情况做出假设：_______-八年级生物
• —Is this pair of shoes Jim's? —It _his.They're too big for him.[ ]A. might be B. can'
• —I still have a toothache. —Oh, sorry, the medicine didn't work, so you ________try another kin
• 研究生态系统的能量流动，可帮助人们合理地调整生态系统中能量流动的关系，使能量_________地流向对人类最有益的部分。-八年级生物
• I_____play the guitar.It's too difficult. [ ]A. canB. can't C. doesn't-七年级英语
• —You see, a man is cutting a tree on the moon. —It _________ be true. The teacher says there is no a