Oracle Database Discussions

I read the Oracle book with some self-tests and was confused with the Test question:
You issue these commands:
A. grant select on hr.regions to jon;
B. grant all on hr.regions to jon;
C. grant dba to jon;
D. grant select on hr.regions to public;
Which grants could be revoked to prevent JON from seeing the contents of HR.REGIONS?
(Choose all correct answers.)
A. a, b, c, and d
B. a, c, and d
C. b, c, and d
D. c and d
E. a, b, and c

I research the commands and found that for prevent user from seeing the contents I have to revoke everything, so my answer was A.
but in book answers I found this:
A, B, and C. Any of these will prevent the access.

D is wrong because the grants in (a) and (b) will remain in effect. E is wrong because the
grant to PUBLIC in (d) will remain in effect.

Since I newbe in Oracle I tried this test manually and it works only if you revoke everything.

Is it book issue(typo) or I was wrong according to B and C ?