Read the following paragraph and underline the topic sentence on the answer sheet.
No one knows exactly who invented knitting. It happened in different areas of the world at different times. The exact origins of knitting are a bit hard to place. Most recorded works say its origins come from the Middle East, which then spread to countries far away via trade routes. Other nations favored the elaborate Arabic-influenced knitting styles. Origins of knitting in Arabic areas can be traced back to fishermen, who would use the technique to create nets. Knitting originated in Egypt somewhere between 500 AD & 1200 AD. The oldest known knitted object and pieces come from Egypt, which are socks from the 1lth century.These socks are quite complex, using a special stitch and detailed color work. In the sametomb where the socks were found, other fragments were present.
【正确答案】： The exact origins of knitting are a bit hard to place.
