Question 17

When mapping a binary relationship $R$ between entity sets $A$ and $B$ into relational tables:

1. Merging with table of A: Merging the relationship relation for $R$ into the relation for entity $A$ means including the primary key of $B$ as a foreign key in table $A$.
2. Cardinality requirement: For every entity instance in $A$, there must be at most one associated instance in $B$ (otherwise, a single row in $A$ would need to store multiple foreign key values, violating 1NF). Therefore, the mapping cardinality from $A$ to $B$ must be many-to-one (many entities of $A$ relate to at most one entity of $B$).
3. Participation requirement: If the participation of $A$ in $R$ is total, every entity in $A$ is guaranteed to participate in $R$, ensuring that the foreign key column in table $A$ will never be NULL.

Hence, the relational table for $R$ can be cleanly merged with that of $A$ when the relationship $R$ is many-to-one (from $A$ to $B$) and the participation of $A$ in $R$ is total. This corresponds to option C.