Explanation : Deadlock Detection.
Always grant resource request when possible. Periodically check for deadlocks. If a deadlock exists, recover from it.
Disallow one of the four necessary conditions for deadlock.
Do not grant a resource request if this allocation have the potential to lead to a deadlock.
Ignore the problem
Makes sense if the likelihood is very low.
Explanation : Atleast one process will be holding 2 resources in case of a simultaneous demand from all the processes. That process will release the 2 resources, thereby avoiding any possible deadlock.