Final answer:
Brianna, who is 18 months old, would be considered difficult to redirect according to Thomas and Chess. This is because she cries frequently, is hard to soothe, and wakes frequently during the night.
Step-by-step explanation:
According to Thomas and Chess, Brianna, who is 18 months old, would be considered difficult to redirect. This is because she cries frequently, is hard to soothe, and wakes frequently during the night, which are characteristics of a difficult temperament. Difficult infants often have strong negative reactions to new stimuli and tend to have irregular feeding and sleeping patterns.