How are cluster$-$head nodes are determined in LEACH $($Low Energy Adaptive Clustering Hierarchy$)$ topology?

$($LEACH assumes that cluster heads can communicate directly with base station$).$

Group of answer choices

Cluster$-$head nodes are fixed, and this position is self$-$elected at different time intervals

Cluster$-$head nodes are fixed, and this position is determined by a local network manager

Cluster$-$head nodes are not fixed, and this position is determined by a local network manager

Cluster$-$head nodes are not fixed, and this position is self$-$elected at different time intervals