Audit alter table - DDL and drop table

I am trying to audit all DDL and table drop statement on one production schema and not working. I only see the first statement the other statement does not show up.
I would like to audit all DDL commands on all tables in a particular schema.

i ran this AUDIT ALTER ANY TABLE;

Statement:

1. ALTER TABLE STORE_APP MODIFY(NBP VARCHAR2(20));  -- this is only one shows up in SELECT * FROM dba_audit_trail.

2. ALTER TABLE STORE_APP ADD (NBP_NEW1 VARCHAR2(10));

3. ALTER TABLE T_STORE_APP DROP COLUMN REGION_ID;

4. ALTER TABLE T_STORE_APP DROP COLUMN REGION_NAME;