题目内容：

As they migrate, butterflies and moths choose the winds they want to fly with, and they change their body positions if they start floating in the wrong direction. This new finding suggests that insects may use some of the same methods that birds use for traveling long distances. Scientists have long thought that insects were simply at the mercy of the wind.

Fascinating as their skills of flight are, migrating behavior has been difficult to study in insects because many long distant trips happen thousands of feet above ground. Only recently have scientists developed technologies that can detect such little creatures at such great heights.

To their surprise, though, the insects weren't passive travelers on the winds. In autumn, for example, most light winds blew from the east, but the insects somehow sought out ones that carried them south and they positioned themselves to navigate directly to their wintering homes.

Even in the spring, when most winds flowed northward, the insects didn't always go with the flow. If breezes weren't blowing in the exact direction they wanted to go, the insects changed their body positions to compensate(补偿, 弥补). Many migrating birds do the same thing.

The study also found that butterflies and moths actively flew within the air streams that pushed them along. By adding flight speeds to wind speeds, the scientists calculated that butterflies and moths can travel as fast as 100 kilometers an hour. The findings may have real-world applications. With climate warming, migrating insects are growing in number. Knowing how and when these pests move could help farmers decide when to spray their crops.

1.What's the main idea of the text?

A．Insects migrate with the seasons.

B．The wind helps insects greatly in migrating.

C．Windsurfing insects have real direction.

D．Scientists have trouble in observing insects.

2.Scientists originally thought that _____.

A．insects always waited for their favorable winds

B．insects chose the winds they wanted to ride

C．insects were just blown about by the wind

D．insects positioned themselves in the winds

3.It is not easy to study the migrating behavior of the insects because ______.

A．the little creatures can fly very fast

B．their flight is long and high above ground

C．the wind's direction is hard to forecast

D．they have no regular migrating courses

4.According to the passage, the findings can ____

A．increase insects in number

B．instruct farmers when to spray their crops

C．prevent climate warming

D．help protect insects