Which Condition Falls

/* thread 1 */                  /* thread 2 */
pthread_mutex_lock(&L1);        pthread_mutex_lock(&L2);
pthread_mutex_lock(&L2);        pthread_mutex_lock(&L1);
/* ... */                       /* ... */

Deadlock requires all four of mutual exclusion, hold-and-wait, no preemption, and circular wait. Select every change below that makes deadlock impossible for this code. More than one applies.