简述滤层产生裂缝的原因。
参考答案：主要是由于滤料层含泥量过多，滤层中积泥不均匀引起局部滤层滤速快，局部滤速慢造成的。
根据《处方管理办法》：复方樟脑酊用于门诊患者处方最大量（）.
A．一次常用量
B．3日常用量
C．5日常用量
D．7日常用量
E．15日常用量
A large manufacturing company is in a competitive industry. It has above-average investment opportunities and its return on investments has been above the required rate of return. The firm retains a large portion of earnings to fund its superior investment projects. The company is best characterized as a.（）
A. growth company.
B. cyclical company.
C. speculative company.
