User A executes the following command to update the TRANS table） SQL> UPDATE B.trans SET tr_amt=tr_amt+500 WHERE c_code=’C005’； Before user A issues a COMMIT or ROLLBACK command， user B executes the following command on the TRANS table： SQl> ALTER TABLE trans MODIFY （tr_type VARCHAR2 （3））； What would happen in this scenario？（）

A. The transaction for user A is rolled back.
B. The ALTER TABLE command modifies the column successfully.
C. The ALTER TABLE command fails due to the resource being busy.
D. The ALTER TABLE command waits until user A ends the transaction.