Activity $D$ on a CPM network has predecessors $B$ and $C,$ and has successor F$.$ D has duration $6.$ B$\text{'}$s earliest finish is $18,$ while C$\text{'}$s is $20.$ F$\text{'}$s late start is $26.$ Which of the following is true?

All of the above are true.

$C$ is completed before $B.$

$D$ is a critical activity with $ES=20$ and $EF=26.$

$B$ is a critical activity.