单项选择题 You are developing an application that will perform mathematical calculations.You need to ensure that the application is able to perform multiple calculations simultaneously. What should you do？（）

单项选择题 Your application uses two threads， named threadOne and threadTwo.You need to modify the code to prevent the execution of threadOne until threadTwo completes execution. What should you do？（）

多项选择题 You create a service application that monitors free space on a hard disk drive.  You must ensure that the service application runs in the background and monitors the free space every minute. What should you do？（）