单项选择题

What does the second paragraph mainly discuss

A．Some animals and plants depend on each other for existence.
B．Some animals and plants develop their relationship easily.
C．Some plants depend on each other for food.
D．Some animals live better together.

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热门试题

单项选择题

Some birds like to sit on a sheep because ______.

A．they can eat its parasites
B．they enjoy traveling with the sheep
C．they depend on the sheep for existence
D．they find the position most comfortable

单项选择题

Which of the following words best describes Mum

A．polite.
B．patient.
C．changeable.
D．clever.