题目内容：

Dodder is an unusual and unwanted plant that attacks other plants. Except for its flowers, the plant looks like spaghetti, a kind of noodles in the shape of long thin pieces that look like string when they are cooked. Its almost leafless, thread-like stems (茎) hang down on top of other plants that dodder needs to stay alive. Dodder does not produce its own food. Instead, it steals food from other plants. It feeds by sucking juices from the plant which is wrapped around, often making its host very weak or even killing it.

Dodder can find other plants by their smell. When a young dodder plant starts growing, it follows the smell of plants it prefers, like tomato plants, potato plants, or other farm crops. Unlike most plants that usually grow in the direction of light or warmth, a dodder plant will grow in the direction of, for example, tomato smell—if a tomato happens to be growing nearby.

However, a young dodder plant must find a host plant quickly. It no longer needs its root once it is attached to the host and wrapped around it. If it cannot catch a smell of a potential host within a few days, it will dry up and disappear—even if there is plenty of water around. Once it finds a host, the young dodder plant will attach itself to it and start growing faster. At that point the dodder plant will drop its root.

Dodder is thus a difficult weed to manage and a real headache for farmers. When it does get out of hand, dodder can greatly reduce a farmer’s harvest or even destroy crops completely. Before sowing their produce, especially farmers in warm parts of the world often check to make sure no unwanted dodder seeds have mixed with their crop seeds. This is a good way to stop dodder plants from making their way to a crop field secretly.

1.Why does the author mention spaghetti in the first paragraph?

A. To analyze the content of some food.

B. To describe the shape of dodder plants.

C. To explain where the dodder plants come from.

D. To argue that dodder plants can be used.

2.What will happen if a dodder plant starts growing where there are no other plants around?

A. It will die sooner or later.

B. It will grow deep roots.

C. It will attract other plants.

D. It will cover the entire area of soil.

3.What can be inferred from the passage?

A. Dodder does not produce its own food.

B. Dodder can affect farmers’ income.

C. Dodder can only survive in the shade.

D. Dodder only grows in the warm areas.

4.What is the main topic of the passage?

A. A new variety of farm crops.

B. Plants that are harmful to humans.

C. The special abilities of a dangerous plant.

D. Recent improvements in farming methods.