综采工作面“四到位”管理制度具体指什么？
参考答案：
即超前拉架到位、护帮板打开到位、支架初撑力到位和跟机拉架到位。
An analyst gathered the following information about a company:Using the dividend discount model and the other data given, the company's stock is best described as a:()
A. growth stock.
B. cyclical stock.
C. speculative stock.
微分方程y"+2y’-15y=0的通解是______。
