The second set of the three permissions (r-) indicates that

In Unix file permissions, the three sets of permissions (rwx) represent the access rights for the owner, group, and others, respectively. The second set of permissions, indicated by (r-), means that the group associated with the file or directory has read permission only. The absence of the "w" (write) and "x" (execute) permissions indicates that the group does not have those permissions.
So, Option B is the correct interpretation of the second set of permissions (r-) in Unix file permissions.