When trying to run topas on an AIX 4.3.x system， the system administrator gets the error message "ksh： topas：  not found."   Which of the following options is the most likely reason this occurred？（）

• A、 The fileset bos.perf.tools is not loaded on this system.
• B、 The fileset perfagent.tools is not loaded on this system.
• C、 The command topas is only available in AIX version 5.x.
• D、 The path variable does not include /usr/samples/kernel/. Either add it to the .profile or cd to that location and run the command again.