叶丝加工要达到成丝率高、纯净无杂质、松散且具有弹性和（）等要求.
A、填充力
B、燃烧性
C、含末率
D、抗碎性
参考答案：A
Mr Lee was so tired that he couldn’t keep his eyes________.
A. open B. closed C. close
从北极点观察地球的自传方向是[ ]
A、自东向西
B、自西向东
C、顺时针转
D、逆时针转
