Jade (玉石) finders played an important role in the invention of the 'ladle'. They travelled great distances to look for jade. in order not to lose directions, they would take a 'ladle' with them. The jade connection is important. Lodestone is a hard material—though not as hard as some jade. And the making of a magnetic 'ladle', as well as a highly smooth stone board, would have required great skill. This suggests that the compass was invented by the jade finders of ancient China. However, the making of a 'ladle' was a tough job. Much work needed to shape a piece of lodestone into a ladle would mean much of its natural magnetism (磁性) had been lost. This again meant that only a few 'ladles' could have been produced. Small numbers of ladies produced and growing need for navigation led to a search for ways to produce more compasses, and at the same time, smaller and better compasses. What is the first paragraph mainly about? A．Columbus was a great sailor and discoverer. B．The compass was invented by Columbus. C．The invention of the compass is important in human history. D．Columbus introduced the compass to the West Indies.