About Question enthuware.oce-ejbd.v6.2.545 :

[sanju.ait@gmail.com]

"A stateless session bean should be prepared to handle multiple client requests simultaneously."

This could be achieved by multiple instances of stateless session bean. Correct wording could be
"A stateless session bean instance should be prepared to handle multiple client requests simultaneously."

[admin]

Updated.
thank you for your feedback!

[himaiMinh]

In option 3 explanation "No enterprise bean needs to be prepared to handle simultaneous client requests...."
I think singleton beans can be prepared to handle simultaneous client requests as some methods in a singleton bean can be annotated with @Lock(READ).