Answer:
4
Step-by-step explanation:
#1 has to be excluded, since it jumps from 4 to 5 and has a hole between x=4 and x=5
#2 loses the extreme values. It would be correct if the domain was [tex]2<x<5[/tex]
#3 is including values in the interval [tex]1<x \leq 2[/tex] which aren't in our domain.
#4 is the remaining one.
