Hi Mini,
Well but if you look at HFE 672 Q46, it doesn't thinks "Primary key fields must be cmp-fields"
Lets see what the spec says about compound primary keys (spec p203 section 10.8.2)
The names of the fields in the primary key class must be a subset of the names of the container-managed fields.
So, now you know that answer to Q46 in HFE is incorrect.
Hope this helps
Suman