下列改变物体运动状态的力是( )
⑴____ A. vacation B. exam C. David D. favorite
⑵____ A. most B. post C. host D. cost
⑶____ A. seem B. feel C. coffee D. between
⑷____ A. however B. blow C. brown D. now
⑸____ A. clearly B. hear C. learn D. near
有机合成材料是材料发展史上一次重大突破。下列物质中,属于有机合成材料的是( )