An ER model of a database consists of entity types A and B. These are connected by a relationship R which does not have its own attribute. Under which one of the following conditions, can the relational table for R be merged with that of A?

When converting an ER diagram into relational schemas:

1. Relationship Cardinality (Many-to-One from A to B): In a many-to-one relationship from entity set $A$ to entity set $B$, each entity in $A$ is associated with at most one entity in $B$. Thus, the primary key of table $A$ can also serve as the primary key of relationship $R$.

2. Participation Constraint (Total Participation of A): If the participation of $A$ in $R$ is total, every entity in $A$ is guaranteed to be related to some entity in $B$. Merging the relationship relation $R$ into table $A$ by adding the primary key of $B$ as a foreign key attribute in table $A$ will never result in NULL values for the foreign key.

3. Partial Participation: If participation of $A$ were partial, merging would introduce NULL values for entities in $A$ that do not participate in $R$.

Therefore, the table for $R$ can be safely merged with $A$ when the relationship $R$ is many-to-one from $A$ to $B$ and the participation of $A$ in $R$ is total.

Hence, (C) is the correct option.