Follow my thought, TXs are not the most difficult part of the exam

:
The cruicial point is method R. The only attribute that allows us to start a new transaction from within the current one is RequiresNew. Thus, we leave out option B, because Mandatory attribute will cause the transaction Foo to be propagated to the method R.
Let's take option C.
R - ok
S - ok
T - ok. As we have TX foo from Method Q, we will re-use it.
U - here we have a problem. Never forces you make a call
without a transaction context. If you call it with a transaction already registered, a RemoteException/EJBException is thrown. Option C goes out.
Option D.
R - ok
S - ok
T - ok
U - a problem. A Supports TX attribute allows the method to run with or without TX context. If there were a transaction already, we would join it. Otherwise we happily run without a transaction at all. Note this is not an option for Entity Beans, where you
always have to run within a transaction context.
What left? Option A, let's check it.
R - ok
S - ok
T - ok
U - ok. Here's the trick. In method U we run without a transaction, but the previous transaction still exists and is suspended.
V - ok. Method U (no TX) calls method V. method V doesn't see the suspended transaction, it sees only what it's caller (U) has. As the attribute is Supports and we have no previous transaction, we do not create one, but run without a TX.
Hope this helps, and you are not lost yet

Please, see section 17.6.2, page 357 of the spec. It has a nice summary table at the end as well.
P.S.: SCBCD seems to be the funniest exams of all by far with all those schemes, drag-n-drops. What other surpises do you guys have in your sleeve?

[ May 28, 2003: Message edited by: Andrew Perepelytsya ]