According to the output of getfacl app, user1 has only " rw " (read and write) permissions, but lacks " x " (execute). Without execute permission, user1 cannot run the file. To allow user1 to execute app, you must update the ACL to add execute permission (e.g., setfacl -m u:user1:rwx app). Modifying " others " permissions (option B) is not secure or necessary, adding user1 to the wheel group (option C) is unrelated, and moving the file (option D) does not resolve permission issues.
Reference:
CompTIA Linux+ Study Guide: Exam XK0-006, Sybex, Chapter 7: " Securing Linux Systems " , Section: " Managing File and Directory Permissions and ACLs " CompTIA Linux+ XK0-006 Objectives, Domain 3.0: Security