(4) If \( A=\{4,2,7\} \) and \( B \subset A \), which of the following can be the set \( B \) ? \( \begin{array}{ll}\text { (a) }\{4,6\} & \text { (b) }\{1,3,5\} \\ \text { (c) }\{4,3,7\} & \text { (d) }\{7,2\}\end{array} \)

To determine which of the options can be the set \( B \) such that \( B \subset A \) where \( A = \{4, 2, 7\} \), we need to check each option to see if it contains only elements that are in set \( A \). 1. **Option (a)**: \( \{4, 6\} \) - This set contains the element \( 6 \), which is not in \( A \). Therefore, this option cannot be \( B \). 2. **Option (b)**: \( \{1, 3, 5\} \) - This set contains elements \( 1, 3, \) and \( 5 \), none of which are in \( A \). Therefore, this option cannot be \( B \). 3. **Option (c)**: \( \{4, 3, 7\} \) - This set contains the element \( 3 \), which is not in \( A \). Therefore, this option cannot be \( B \). 4. **Option (d)**: \( \{7, 2\} \) - This set contains only the elements \( 7 \) and \( 2 \), both of which are in \( A \). Therefore, this option can be \( B \). Thus, the only valid option for the set \( B \) is: **(d) \( \{7, 2\} \)**.