Which of the following statements is correct? O a$.$ K$-$means clustering requires the number of clusters be specified before computation starts. O b$.$ Hierarchical clustering $($e$.$g$.,$ single linkage$)$ requires the number of clusters be specified before computation starts. O c$.$ Both $($a$)$ and $($b$)$ are true. O d$.$ Both $($a$)$ and $($b$)$ are false