Java EE (Java Enterprise Edition) General Discussion

Hi all,
I'm learning to SCBCD 5.0 cert. Now I'm doing some example questions. And I have a problem with it. I know what is the correct answer.., but I'd like to understand..
why the rest is incorrect. If someone could explain that to me.., that would be great. (ex. Answer c - Incorrect because............)

Question:
A developer writes a stateless session bean with one local business interface and with container-managed transactions. All business methods have transaction attribute REQUIRED. The bean has an injected field sessionCtx of the type SessionContext. Which two operations are allowed in a business method of the bean ? (choose two):
a) sessionCtx.getEJBObject
b) sessionCtx.setRollbackOnly
c) sessionCtx.getMessageContext
d) sessionCtx.getBusinessObject
e) sessionCtx.getEJBLocalObject

Thanks a lot. (Please don't give me correct answer.., I know this one.., but explanation.., why A is incorrect..., ans so on)
Regards,
Pawel