下面四句话哪句是错无的?
A: Singleton sao; the objects are instantiated on the server as soon as the client creats the object.
B: SingleCall sao; the object is instantiated on the server when the first method is called for that object.
C: Singleton sao; only one instance on the server will be created to service all calls to the object.
D: SingleCall sao; a new instance of the object will be created to servce each call.