To solve the given set problems, we need to perform set operations such as intersection, union, and complement.
(a) To find \( B \cap D^{\prime} \), we first determine the complement of set \( D \) with respect to the universal set \( U \), and then find the intersection of set \( B \) with this complement.
(b) To find \( (B \cup D)^{\prime} \), we first find the union of sets \( B \) and \( D \), and then determine the complement of this union with respect to the universal set \( U \).
To find the complement of set \( D \) with respect to the universal set \( U \), we calculate:
\[
D^{\prime} = U - D = \{f, k, m, q, r, x, z\} - \{f, m, r, z\} = \{q, k, x\}
\]
Next, we find the intersection of set \( B \) and the complement of \( D \):
\[
B \cap D^{\prime} = \{k, r, z\} \cap \{q, k, x\} = \{k\}
\]
We then calculate the union of sets \( B \) and \( D \):
\[
B \cup D = \{k, r, z\} \cup \{f, m, r, z\} = \{f, k, m, r, z\}
\]
Finally, we find the complement of the union \( B \cup D \) with respect to \( U \):
\[
(B \cup D)^{\prime} = U - (B \cup D) = \{f, k, m, q, r, x, z\} - \{f, k, m, r, z\} = \{q, x\}
\]
Thus, the answers to the questions are:
- (a) \( B \cap D^{\prime} = \{k\} \)
- (b) \( (B \cup D)^{\prime} = \{q, x\} \)
\[
\boxed{(a) \{k\}, (b) \{q, x\}}
\]