单项选择题
A．One kind of animals is eaten up. B．One kind of plants is destroyed. C．One kind of animals eats another. D．One of the links is destroyed.
A．from water B．from the air in the sky C．from the soil D．from water, things in the soil and air and sunlight
A．Each plant can live alone. B．Each animal can live alone. C．Everything living on earth cannot live without needing other living things. D．If living things want to live they must kill each other.