yes, that is alos correct.
see "Table 12 Container’s Actions for Methods of Beans with Bean-Managed Transaction".
If the transaction associated with the instance is T1, then business called will be execuated in same transaction.
There will not be new transaction, if you tried to create one, you will get javax.transaction.NotSupportedException in the begin
following lines from MK's study guide
"A stateful session bean instance may, but is NOT REQUIRED to, commit a started transaction before a business method returns. If a transaction has not been completed by the end of a business method, the container retains the association between the transaction and the instance across multiple client calls until the instance eventually completes the transaction. "