Answer
$6$
Work Step by Step
The number of ways to select the second sentence: $3$ (any of them can be apart from the last and the already selected first sentence)
The number of ways to select the third sentence: $2$ (any of them can be apart from the last and the already selected first and second sentence)
Then the fourth sentence is the one that is not the first, second, third or last.
The first and last sentence is fixed.
Number of different ways to schedule the appearances:$3\cdot2\cdot1\cdot1=6$
