在一个生态系统中，食物链中的能量逐级减少最主要的原因是(　    )

给下列句子选择恰当的答语。⑴Where is classroom 4？ ____    A．It's next to the art room.
⑵This is my school.____           B．Yes，it is.
⑶Is this the teachers' office?____  C．It's so beautiful!
⑷Do you have a library?____      D．Yes，we do.
⑸Where is the gym?____          E．Classroom 4 is under the art room.

下列物质的水溶液能导电，但属于非电解质的是           （  ）

—________ Mr Li ________ Rose Garden School?

—Yes, he is.

亚洲与北美洲分界线是（    ）