Kite flying is the sport of send

Kite flying is the sport of sending up into air, by means of the wind, light frame covered with paper, plastic or cloth. The frame can be one of many different shapes and is attached to a long string held in the hand or wound on a drum. Kites have a long history in practical application and many different types of kite have been developed to serve various purposes.
The ancient Chinese used bird-kites to carry ropes across rivers and valleys. The current folding kite which will dive excitingly is an improved type of such a kite. With its long flat body and single pair of bird-like wings, it looks just like a large bird in the air. The moder version is usually made of tissue paper rather than the traditional silk.
Man-lifting kites were developed in ancient times, again by the Chinese, for getting information from walled cities and army camps. In fact, as recently as World War, German U-boats flew kites from their towers to lift people into the air to watch the land. These kites, which are no longer in existence, were made of lightweight cloth. They were much larger and stronger than the Chinese ones. Their design, however, was simply that of the cutter kite. Smaller in size,this type of kite is still very popular as toy for children, being easy to make with a diamond-shaped- frame, no wings and brown-paper- covering.
Box kites are another type of kite found in toy shops today. The first box kite, named for its box-like body, was developed in the nineteenth century to test theories of flight and this type of cotton-covered kite greatly assisted the success of early airplanes. These kites are the ancestors of a heavier version of the box kite, called the double box kite, which consists of two main sections,placed side by side. Developed for the peacetime purpose of fishing in strong sea wind, it is the only modern kite described which has practical value. A long-lasting plastic material has to be used for this kite, which carries fishing lines.
The ancient Chinese man-lifting kites were used ______.
A、to carry ropes across rivers and valleys
B、for the military purpose
C、as toys for children
D、for fishing in strong sea wind
【正确答案】：B