下列关于地球圈层结构的叙述，正确的是（）
A.岩石圈包括地壳和整个地幔
B.大气圈的主要成分是氮和氧
C.生物圈是地球上所有生物的总称
D.水圈是连续而又规则的圈层
参考答案：B
解析：
岩石圈包括地壳和上地幔顶部，A错误；大气圈的主要成分是氮和氧，B正确；生物圈是地球上所有生物及其生存环境，C错误；水圈是连续的，但是不规则，D错误。
考点：地球的圈层结构。
There are many things that you should be careful with when you are alone at home. Read the following situations 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 you don't know how to use them, ask your parent. 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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