A、Animals. B、Droppings. C、Fruits. D、Winds. A短文最后提到Most…depend on animals to eat their fruits and spread their seeds，即树木主要是通过动物吃它

Most rain forests lie close to the equator, where the climate is often mild and there are long hours of sunshine. The warmth of the land heats the air above, causing it to rise and tiny drops of water to fall as rain. The rainfall can reach at least 98 inches a year. This wet, warm world with plenty of sunlight is perfect for plants to grow, so the trees grow fast with green leaves all the year round. The trees themselves also have an effect on the climate. They gather water from the soil and pass it out into the air through their leaves. The wet air then forms clouds, which hang over the tree tops like smoke. These clouds protect the forest from the daytime heat and nighttime cold of nearby deserts, keeping temperatures fit for plant growth.
    Rain forests slightly farther away from the equator remain just as warm, but they have a dry season of three months or more when little rain falls. Tree leaves fall during this dry season and new leaves grow when the wet season or monsoon(rainy season)begins. Thus these areas are known as the "monsoon forest".
    Another type of rain forest grows on tropical mountains. It is often called the "cloud forest" because clouds often hang over the trees like fog.
    The rain forest is the ideal place for the growth of many different trees. Most of them depend on animals to eat their fruits and spread their seeds. When the fruits are eaten, the seeds inside them go undamaged through the animal’s stomachs and are passed out in their droppings. The seeds lying on the forest floor then grow into new trees.
Questions 19 to 21 are based on the passage you have just heard.
19. What do we know about the climate of the rain forests near the equator?
20. What can we learn from the passage?
21. Which plays the most important role in the spreading of seeds according to the passage?