问题
填空题
大气中的氧气、二氧化碳、水等物质会随着大气在全球范围内活动，不会局限在某一个生态系统，这个现象说明___________。
答案
地球上各个生态系统之间不是孤立的，而是有着密切联系。
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大气中的氧气、二氧化碳、水等物质会随着大气在全球范围内活动，不会局限在某一个生态系统，这个现象说明___________。
地球上各个生态系统之间不是孤立的，而是有着密切联系。
There are many things that you should be careful with when you are alone at home. Read the following solutions to protect yourself. Keep the door locked when you are alone at home. Many people think it’s the best way to protect themselves. Keep a list of phone numbers to call for help-such as 110, the police station or a neighbor’s number. Be careful with the electrical appliances（电器）. If don’t know how to use them, ask your parents. Make a safety check before going to sleep. Look through the keyhole when you hear the doorbell. If there are strangers, ask “Who’s that?” with the door locked and say “Come back later.” Don’t tell them that your parents are away. Say “Mum’s having a shower.” or “Dad’s having a sleep.”
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