$1-$ Consider the schedules S$1,$ S$2,$ and S$3$ below. State whether each schedule is strict, cascadeless, and recoverable. Explain your reasons. If a schedule is recoverable$/$cascadeless$/$strict you need to explain why it is so$,$ but it is acceptable if you give a non$-$question$-$specific generic reason. However, if a schedule is not recoverable$/$cascadeless$/$strict$,$ you need to specify the exact reason why it is not, by giving an example from the schedule itself $($a single correct example is enough$).$

$-$ S$1$: R$1($A$)$; R$4($A$)$; W$2($B$)$; W$4($C$)$; R$3($A$)$; R$2($D$)$; C$2$; R$1($D$)$; R$3($B$)$; C$3$; W$1($C$)$; C$1$; C$4$;

$-$ S$2$: W$1($B$)$; W$3($A$)$; W$2($C$)$; R$3($C$)$; C$1$; W$2($D$)$; R$2($B$)$; W$4($B$)$; R$3($A$)$; A$2$; W$4($D$)$; R$3($D$)$;

C$4$; W$3($A$)$; C$3$;

$-$ S$3$: W$2($C$)$; R$3($C$)$; R$1($B$)$; W$2($C$)$; W$2($D$)$; R$2($B$)$; W$4($B$)$; R$3($A$)$; W$4($C$)$; C$4$; R$1($B$)$; W$1($A$)$; C$1$; C$2$; C$3$;