Help with my sql

I have a test table
SQL> select * from test;

COL1 COL2 COL3 COL4
---------- ---------- ---------- ----------

a          b          c                   1
a          b          c                   1
a          b          c                   2
a          b          c                   3
a          c          b                   1

For each combination of col1,col2, and col3, I just want the one with the max(col4).

but when i

SQL> select * from test
  2 where col4 in (
  3 select max(col4) from test
  4 group by col1,col2,col3);

COL1 COL2 COL3 COL4
---------- ---------- ---------- ----------

a          b          c                   1
a          b          c                   1
a          c          b                   1
a          b          c                   3

I still got two unwanted rows, which is row no1 and row no2.

How could i eliminate the first two rows?

Thanks for your help.  

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