垂直的需求曲线的价格弹性一定等于无穷大。
曲状元
public class MyLogger { private StringBuilder logger = new StringBuuilder（）； public void log（String message， String user） { logger.append（message）； logger.append（user）； } } The programmer must guarantee that a single MyLogger object works properly for a multi-threaded system. How must this code be changed to be thread-safe？（） [" synchronize the log method"," replace StringBuilder with StringBuffer"," No change is necessary， the current MyLogger code is already thread-safe."," replace StringBuilder with just a String object and use the string concatenation （+=） within the log method"]
学前儿童音乐课程内容组织有哪三种形式？
简述近现代中外秘书理论与实践发展的相同之处。
简述气-水联合反冲洗工艺原理
