U$.$S$.$ Border Patrol Agents were the original Air Marshals. In $1961,$ there were four hijacking attempts on U$.$S$.$ commercial aircrafts. In August of $1961,$ President Kennedy announced that U$.$S$.$ Border Patrol Agents would be deployed to prevent future hijackings; $12$ hours later, Border Patrol Agents were guarding their first flight. The Miami Sector coordinated the operation for flights originating throughout the nation. The operation, which ended in October $1961,$ was successful in that no hijackings were attempted during the operation.

A$)$ at least some hijacking attempts were made when Border Patrol Agents guarded commercial flights

From the information given above, it can be validly concluded that, in $1961,$

B$)$ every hijacking attempt occurred at a time other than when Border Patrol Agents guarded commercial flights

E$)$ all hijacking attempts were made when Border Patrol Agents guarded commercial flights