the problem of condition process

[skysea]

Hi,everyone:
    I defined a process that has three activities(A,B,C),and a variables(parm).when executed activity A,if parm equals "aa", the next step of the process will execute activity B.Else it will execute activity C.The problem is when I set "aa" to parm,the process also execute activity C.why? I need you helping.

Regards!

c_workflow.xpdl